The word fungus [ˈfʌŋɡəs] refers to a ‘group of spore-producing organisms which feed on organic matter’ which includes molds, yeast, and mushrooms, among other types (Concise Oxford English Dictionary, COED). Some dictionaries give a more thorough definition for the word fungus, such as the following one from the American Heritage Dictionary:
any of numerous spore-producing eukaryotic organisms of the kingdom Fungi, which lack chlorophyll and vascular tissue and range in form from a single cell to a mass of branched filamentous hyphae that often produce specialized fruiting bodies. The kingdom includes the yeasts, smuts, rusts, mushrooms, and many molds, excluding the slime molds and the water molds (AHD).
Notice that this much more explicit definition neglects to mention the fact that these organisms feed on organic matter, which COED’s much briefer definition deems important to mention.
Linnaeus was the 18th century Swedish botanist who came up with the modern binomial nomenclature that is the basis of modern taxonomy in botany and zoology and initially he classified fungi as part of the plant kingdom. More recently, however, fungi were moved to a kingdom of their own since their cells have unique characteristics, such as the lack of chlorophyll and unique components in the cell wall and cell membrane.
Nobody really knows how many species of fungi there are and estimates vary greatly, from 1.5 million to 12 million, of which only about 140,000 have been studied and described. In addition to the organisms that scientists fit into this biological kingdom, there are also funguslike organisms, such as slime molds and water molds (oomycetes), that do not belong to kingdom Fungi but are often popularly (as opposed to scientifically) called fungi. In recent times, they have recently been moved to a separate biological kingdom: kingdom Protista (see below). Fungi are extremely important since, together with bacteria, they break down organic matter in the soil, making plant growth possible. Also, they are crucial for many basic things important to humans, such as the making of bread, wine, and beer. In addition, we should not forget that some fungi are pathogenic to plants (about 8,000 species) and to humans (about 300 species).[i]
As we saw in the AHD definition above, a fungus is a eukaryotic living organism, that is, one whose cells contain a nucleus. Biologists divide living organisms into two major types, eukaryotes and prokaryotes (eukaryotic and prokaryotic organisms), depending on whether they have nuclei or not. The words prokaryote and eukaryote were created in French by Éduard Chatton in 1925, though they were not adopted in English and Spanish until much later when the concepts were generally accepted in the scientific community. (The Spanish equivalents are procariota or procarionte and eucariota or eucarionte, repectively.) Fr. prokaryote was formed in scientific Latin from Ancient Greek parts: πρό (pró) ‘before’ (pro‑), κάρυον (káruon) ‘nut, kernel’ (‑kary‑), and a suffix derived from Ancient Greek -ώτης (-ṓtēs) (‑ote) from which various kinds of nouns were derived, in particular nouns indicating origin. The first part of the word eukaryote, eu‑ comes from Ancient Greek εὖ‑ (eû), combining form of ἐΰς (eǘs) ‘well, good, true’.
The term prokaryote, pronounced [pɹoʊ̯ˈkʰæɹioʊ̯t] or [pɹoʊ̯ˈkʰæɹiət] in English, is a noun that means ‘single-celled organism with neither a distinct nucleus with a membrane nor other specialized structures’ (COED). The derived adjective is prokaryotic, formed with the Latinate suffix ‑ic. The two types of prokaryotes are bacteria and archaea. The name of the domain, superkingdom, or empire to which the prokaryotes belong is known in English as Prokaryota. In Spanish, the name of the domain is also Prokaryota. Spanish has no name (noun) for the organisms but rather has an adjective, which has two variants, namely procariota or procarionte to refer to such organisms. This adjective is used with a noun as in, organismo procariota/procarionte ‘n. prokaryote’.
The noun eukaryote means ‘organism consisting of a cell or cells in which the genetic material is DNA in the form of chromosomes contained within a distinct nucleus’ (COED).[ii] The word is is pronounced [juˈkʰæɹioʊ̯t] or [juˈkʰæɹiət] in English. Eukaryotes are thought to have derived about two billion years ago from a fusion or symbiotic association of archaean cells and bacteria, so that the latter became engulfed by the former, becoming mitochondria and chloroplasts. The scientific name of the domain, in both English and Spanish, is Eukaryota or Eukarya, also New Latin names. As in the case of prokaryotes, Spanish has no name (noun) for the eukaryotic organisms but rather has an adjective, which has two variants, namely eucariota or eucarionte, to refer to them, so that the way to refer to an eukaryote in Spanish is organismo eucariota/eucarionte.
Fungi, like plants and animals, are eukaryotic organisms, each conforming a separate kingdom of living organisms. Interestingly, fungi are closer to animals than to plants from an evolutionary point of view. However, as we already saw, until molecular methods of analysis of the evolution of organisms (phylogenetic analysis) were introduced, fungi were classified as plants, members of the kingdom Plantae. The reclassification was suggested as recently as 1969 by American plant ecologist Robert Whittaker.
Figure 1 below shows the different kingdoms or domains of living organisms, grouped into the two superkingdoms or domains Prokaryota and Eukaryota. As you can see, fungi, plants and animals, along with protista (see below), are the Eukaryotic kingdoms and bacteria and archaea the prokaryotic ones.
Figure 1: Phylogenetic and symbiogenetic tree of living organisms, showing a view of the origins of eukaryotes and prokaryotes [iii]
The technical terms in Figure 1, with an initial capital letter, are all Neo-Latin ones. We have already explained the origin of the domain names Prokaryota and Eukaryota. Some of the kingdom names are easy to understand since they have cognates in both English and Spanish. One of them is Plantae, nominative plural wordform of Lat. planta ‘sprout, shoot, cutting’, source of Eng. plant and Sp. planta. Another is Animalia, taken from the nominative plural wordform of Lat. animal, source Eng. animal and Sp. animal. Lat. animal is a noun derived by conversion (without affixes) from the adjective animale, neuter of animālis, derived from the noun anima ‘breath, spirit’ (source of Sp. alma ‘soul’).
The additional terms in Figure 1 require some explanation. The name of the domain Bacteria is a New Latin term adapted from Ancient Greek βακτήριᾰ (baktḗria), plural of βακτήριον (baktḗrion) ‘staff, stick’. The singular New Latin wordform is bacterium. English dictionaries tell us that in English too bacteria [bæk.ˈtʰɪɹi.ə] is the plural of a singular form bacterium. This singular wordform is much less commonly than the plural bacteria, however, much like data, also supposedly a plural, is much more common than its presumed singular form datum, which not many speakers know or use. Note that in Spanish, the noun Sp. bacteria is singular, e.g., una bacteria, and its plural is fully regular, namely bacterias, e.g., dos bacterias. In scientific terminology, Lat. Bacterium (with a capital B) is used as the name of the domain to which all bacteria belong. These single cell organisms were given this name by German naturalist Christian Gottfried Ehrenberg because of the rod-shape of the first bacteria that were observed under a microscope, first by Dutch microscopist Antonie van Leeuwenhoek in the 17th century. To this day, bacteria are classified by shape into five groups: spherical (cocci), rod (bacilli), spiral (spirilla), comma (vibrios), and corkscrew (spirochaetes).
The next word in Figure 1 is Protista [pɹoʊ̯ˈtʰɪstə], which is the same in Spanish, pronounced [pɾo.ˈt̪is.t̪a]. This is a technical New Latin term in biology for a type of living organism, though it is much less common than the word bacteria and is also unfamiliar to most people. It was created in latter part of the 19th century. In English, Protista is a plural noun, like bacteria, one used in biology to refer to ‘a major taxonomic group and especially a kingdom comprising the protists’, which are ‘eukaryotic organisms that are unicellular and sometimes colonial or less often multicellular and that typically include the protozoans, most algae, and often some fungi (as slime molds)’ (MW). The words Protista (Sp. Protista) and protist (Sp. protista) are New Latin, from a plural word taken from Ancient Greek πρώτιστᾰ (prṓtista), neuter plural form of πρώτιστος (prṓtistos) ‘very first’, superlative of πρῶτος (protos) ‘first’, formed with the superlative suffix ‑ιστος (-istos).
The word Archaea refers a domain of ‘microorganisms… including especially methane-producing forms, some red halophilic forms, and others of harsh hot acidic environments (as a hot spring)’ (MWC).[iv] This is also a scientific New Latin word, created very recently, in 1990. It is derived from Ancient Greek ἀρχαῖα (arkhaîa) ‘ancient’, neuter plural of the adjective ἀρχαῖος (arkhaîos) (cf. Eng. archaic, archaelogy, and Sp. arcaico, arqueología). In English, Archaea is pronounced either [ɑɹ.ˈkʰi.ə] or [ɑɹ.ˈkʰeɪ̯.ə]. The name of the domain in Spanish is the same, Archaea, since it is a New Latin word, but Spanish has adapted this word as the noun arquea [aɾ.ˈke.a] to refer to the organism. A variant of this name is árquea [ˈaɾ.ke.a], with word-initial stress and both accentuation patterns are considered correct.
Interestingly, fungi are more closely related to animals than to plants or bacteria (see Figure 1). Some biologists believe that the animal and fungus eukaryotic kingdoms should be joined into a common group or clade, the fungi/metazoa group, also known as opisthokonts (Sp. opistoconto), from Ancient Greek ὀπίσθιος (opísthios) ‘rear, posterior’ and κοντός (kontós) ‘pole, etc.’, referring to the flagellum that the sperm of most animals and the spores of some fungi use to propel themselves.[v]
Bacteria often feed on fungi and so the latter have ended up producing antibiotic substances to deal with them. An antibiotic is ‘a substance produced by or a semisynthetic substance derived from a microorganism and able in dilute solution to inhibit or kill another microorganism’ (MWC). The noun/adjective antibiotic (Sp. n. antibiótico, adj. antibiótico/a) is another term formed from classical word parts, this one in French in 1889, by French mycologist Jean Paul Vuillemin, as antibiotique, and from there borrowed into English and Spanish. The word’s two main parts are the Ancient Greek prefix ἀντι‑ (anti‑) ‘against’ and the also Ancient Greek ancient Greek adjective βιωτικός (biōtikós) ‘of life’, derived from the noun from βίος (bíos) ‘life’ by means of the adjective-forming Ancient Greek suffix ‑ικ‑ός (-ik‑ós). The word part βιωτικός (biōtikós) was first borrowed into a European language in the late 18th century in the German borrowing Makrobiotik (1796). From there, this word part was borrowed into English as ‑biotic, French as ‑biotique, and Spanish as ‑biótico/a.
Most natural antibiotics are produced by fungi, but also by bacteria, and most of the targets are bacteria. The first antibiotic discovered by humans, penicillin, is ‘an antibiotic produced naturally by certain blue molds, now usually prepared synthetically’ (COED) and it is ‘used to treat infections caused by bacteria’ in humans (LDCE). The name penicillin [ˌpʰɛnəˈsɪlɪn] (Sp. penicilina) was created in the 1920s from the name of the genus of molds Penicillium that naturally produce this substance, by changing the suffix ‑ĭum for the suffix ‑in‑ used in chemistry and biochemistry ‘to form the names of discrete substances extracted from living organisms or their products’ (OED). The genus name Penicillium [ˌpʰɛnəˈsɪliəm] was derived (in the first half of the 19th century) from the Latin noun pēnĭcillum ‘painter's brush or pencil’ with the suffix ‑ĭum used in taxonomy, referring to the chains of conidia in these organisms that resemble a broom. Lat. pēnĭcĭllum is itself a diminutive of pēnĭcŭlus ‘a brush for removing dust (for which ox-tails and horse-tails were used)’ (L&S). This Latin word is the source of Eng. pencil (from French pincel) and Sp. pincel ‘brush’.
Fungi can be divided into three major types according to their function or how they receive nutrients, which must be come from other organisms rather than created, as plants do through photosynthesis. In this, fungi are like animals. The first type are the saprotrophic fungi, which feed on decaying organic matter, such as by decomposing dead forest matter, either dead trees or dead plant matter scattered over the forest ground. The adjective saprotrophic [ˌsæpɹəˈtʰɹɒfɪk] (Sp. saprotrófico/a) can be seen as derived from the noun saprotroph ‘an organism that feeds on or derives nourishment from decaying organic matter’, though actually the noun (1963) is a back-formation from the adjective, which was created first (1942), in English, from Greek word parts (cf. Part I, Chapter 5). The word saprotroph is formed from the roots of the Ancient Greek words σαπρός (saprós) ‘putrid’ and τροφή (trophḗ) ‘nourishment’. Many edible mushrooms such as morels and shiitake are saprotrophs.
The second type of fungi are the mycorrhizal ones, which form mutualistic symbiotic relationships with plants from which both organisms benefit. The adjective mycorrhizal [ˌmaɪ̯koʊ̯ˈɹaɪ̯zəɫ] (Sp. micorrícico/a) is derived from the noun mycorrhiza [ˌmaɪ̯koʊ̯ˈɹaɪ̯zə] (Sp. micorriza), a late 19th century New Latin word formed from the Ancient Greek roots of the words μύκης (múkēs) ‘fungus’ and ῥίζα (rhíza) ‘root’ (the ‑o‑ is a linking vowel: myk‑o‑rrhiza). The noun mycorrhiza is attested in English in 1886 and the adjective mycorrhizal, formed by adding the Latinate adjectival suffix ‑al, by 1900 (OED). About a third of all mushrooms, such as truffles and chanterelles, are mycorrhizal fungi which coat the fine roots of certain types of trees. These fungi receive sugar from the plant produced by photosynthesis and at the same time they provide the plant with nutrients such as nitrogen and phosphorus which they take from the soil. Additionally, mycorrhizal fungi may protect trees from pollutants.
The third main type of fungus is parasitic fungi, which grow within living organisms at the expense of their hosts, which can be living trees, plants, other mushrooms, or even animals, including humans. In other words, the parasitic fungus benefits from this relationship, but not so the host, which is robbed of nutrients by the fungus and may eventually be killed by it. The adjective parasitic (Sp. parasítico/a) is related to the noun parasite (Sp. parásito). The adjective comes from Lat. părăsītĭcus/a/um (părăsīt‑ĭc‑us), derived by means of the suffix ‑ĭc‑ from the noun părăsītus (părăsīt‑us), which meant first of all ‘guest’, but also ‘in particular, in a bad sense, one who, by flattery and buffoonery, manages to live at another’s expense, a sponger, toad-eater, parasite (syn. scurra)’ (L&S). This Latin noun is a loanword from Ancient Greek παράσιτος (parásitos) ‘one who eats with another’ (L&S), derived by conversion (without affixes or other changes) from the identical adjective meaning ‘that feeds beside’, from παρά (pará) ‘beside’ and σῖτος (sîtos) ‘food’.
There are some types of fungi that were thought to be parasitic, that live within the body or cells of plants but whose relationship to the host is still not well understood and some may be mutually beneficial. These are organisms are known in botany as endophytes [ˈɛndəˌfaɪ̯t] (Sp. endófito), a type of endosymbiont or endobiont.[vi] Actually, some endophytes are bacteria, not fungi, so there are bacterial endophytes and fungal endophytes (Sp. bacterias endófitas, hongos endófitos). The word endophyte is formed from the combining morpheme end(o)‑ of the Ancient Greek adverb ἔνδον (éndon) ‘in, within; inner, internal’ and the combining morpheme ‑phyte taken from Ancient Greek φυτόν (phutón) ‘plant’.
As we saw, some fungi are pathogenic in humans and other animals. The most common fungal diseases or mycoses (Sp. micosis, enfermedad fúngica, enfermedad fungosa, or enfermedad micótica) are (1) fungal nail infection, under fingernails or toenails (medical terms: onychomycosis or tinea unguium) (Sp. infección micótica de las uñas, uñas con hongos); (2) athlete’s foot (tinea pedis) (Sp. pie de atleta), which affects the skin on the feet and can spread to toenails and hands; (3) jock itch (tinea cruris), in the groin and thighs (Sp. tiña inguinal, comezón de deportista); (4) ringworm (tinea corporis), a fungal skin infection that may look like a circular rash (Sp. tiña); (5) yeast infection caused by the yeast Candida albicans, which can be in the vagina (vaginal candidiasis), but also the skin (Cutaneous candidiasis), mouth, gastrointestinal tract, or urinary tract (Sp. infección por hongos, candidiasis, infección por candida, infección por levaduras, micosis,· infección fúngica).
 Eng. smut or smut fungus refers to ‘any fungus of the order Ustilaginales’ (WNTIU). The Ustilaginales are ‘an order of Basidiomycetes’ (Chambers). Smuts are ‘parasitic on plants, causing smut and bunt’ (Chambers). Eng. rust in botany refers to a fungus that causes a plant disease also known as rust which is characterized by reddish-brown spots.
 As usual, every dictionary chooses to include and to omit different facts in their definitions of one and same sense of a word. Some dictionaries still define fungi as being plants, e.g.: ‘a simple type of plant that has no leaves or flowers and that grows on plants or other surfaces. mushrooms and mould are both fungi’ (Longman Dictionary of Contemporary English, LDCE, https://www.ldoceonline.com/dictionary/fungus, 2022.02.17).
 According to Encyclopedia Britannica, ‘[t]ogether with bacteria, fungi are responsible for breaking down organic matter and releasing carbon, oxygen, nitrogen, and phosphorus into the soil and the atmosphere. Fungi are essential to many household and industrial processes, notably the making of bread, wine, beer, and certain cheeses.’ (EB).
 This pro‑ should not be confused with Lat. prō ‘in favour of, on behalf of, etc.’ and Lat. prō or pro ‘forward’.
 A number of English and Spanish words that descend from Ancient Greek had this ‘prefix’ in the original, e.g., Eng. euphemism ~ Sp. eufemismo, Eng. euphoric ~ Sp. eufórico/a, Eng. eulogy (Sp. panegírico) ~ Sp. elogio, Eng. eucalyptus ~ Sp. eucalipto, and Eng. evangelium ‘gospel’ ~ Sp. evangelio.
 The terms prokaryote and Prokaryota were the original ones created by Édouard Chatton in 1925. The term Prokarya was created later, originally as the plural of the word prokaryon created in 1957 to refer to ‘The structure in a prokaryote which contains the genetic material; the prokaryotic ‘nucleus’’ (OED). By analogy with prokaryon (see above), the word eukaryon was created in 1967 to refer to ‘The highly organized nucleus, bounded by a nuclear membrane, that is characteristic of a eukaryotic cell’ (OED), and from the plural of this term, the variant Eukarya for the taxonomic name of the eukaryotes (along with Eukaryota).
 There are eight major taxonomic ranks in biology, of which kingdom is the third one. The ranks are the following: life, domain, kingdom, phylum (pl. phyla), class, order, family, genus (pl. genera), and species.
 In this, bacterium and bacteria in English are like other pairs of fancy Latinate English words are, such as memorandum-memoranda, stratum-strata, datum-data, and curriculum-curricula. Note that most dictionaries have an entry for sing. bacterium, but even more have an entry for plural bacteria. Some only have an entry for bacteria and not for bacterium, such as the Oxford Advanced Learner’s Dictionary.
 Makrobiotik (1796) originally meant ‘inclined or tending to prolong life; relating to the prolongation of life’ (OED). The prefix macro‑ comes from the Ancient Greek adjective μακρός (makrós) ‘long’, cognate with Eng. meager, cf. Old English mæġer ‘meager, lean’, and Sp. magro/a ‘lean’, from Lat. macrum/am (nom. macer/macra).
 Note, however, that the noun saprotroph is attested in German by 1912 (OED). As for the suffixoid ‑trophic, it is commonly used in biology to form ‘adjectives relating to forms of nutrition and feeding’ and in physiology to form ‘adjectives relating to the stimulation of growth or function of an organ or tissue, and designating hormones and other substances acting in this way’ (OED).
 The nitrogen that is characteristic of legume plants is produced by bacteria known as rhizobia that form nodules in the plants’ roots in cooperation with the plant which absorbs the nitrogen from the air first.
 The noun tinea [ˈtʰɪniə] (Sp. tiña) is the technical name for ‘any of several fungal infections of the skin; especially: ringworm’ (MWC). The word comes from Lat. tĭnĕa ‘a gnawing worm, moth, bookworm’. Spanish also has the adjective tiñoso/a, equivalent to Eng. scabby or mangy in Medicine. This Spanish adjective can also mean ‘mean, stingy’ in popular speech.
 In English, the term candida is used for ‘any of various fungi of the genus Candida that are found especially on the skin and in the mucous membranes of the mouth, intestinal tract, and vagina and that may become pathogenic, such as C. albicans, the causative agent of thrush’ (AHD). The genus name Candida and the noun candida for the diseases it causes is New Latin (1939) taken from the feminine form of the Latin adjective candidus/a ‘white’. Eng. thrush (Sp. candidiasis) refers to ‘a contagious disease caused by a fungus, Candida albicans, that occurs most often in infants and children, characterized by small whitish eruptions on the mouth, throat, and tongue, and usually accompanied by fever, colic, and diarrhea’ (AHD).
[iii] Source: By Maulucioni y Doridí - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=25888693 (2021.12.27)