Growth

Here on The Consumerist is a story that evokes no sympathy in me, because apparently I'm a heartless bastard. One of the comments:

Oh Christ dogs are fungible just get another Mandy and keep feeding her more pet meds!

I find that hilarious, because, as I said, heartless bastard, and also the word "fungible" intrigues me. It looks so much like "fungi"! And yet it cannot have anything to do with it!

"Fungible" is from the Latin "fungi vice", "to perform in the place of"; a fungible thing is one that is completely replaceable by another. It seems to have left no other offspring in English. "Fungi", on the other hand, is the plural of "fungus", a word too well-known to require me to try to define it; that word is apparently descended from Greek "spongos" or "sphongos", "sponge", from the spongy massed quality of many fungi such as yeasts and molds.

"Fungous", by the way, is the adjectival form of "fungus", another of those adjective/noun pairs like "mucous/mucus" and "callous/callus", one more thing to confuse people.

There doesn't seem to be a list of such words anywhere; there probably is, because people will make lists of anything, but since I can't find one and there mightn't be one, I decided to compile one myself. Here, and I make no promises as to its absolute completeness (though I tried), is (scroll down)

A list of word pairs in which the noun ends in "-us"
and the adjective in "-ous"

acinus	acinous	a berry
calculus	calculous	a stone
callus	callous	a thickened patch of skin
cumulus	cumulous	a pile: a piled-up cloud
cirrus	cirrous	a tendril: a wispy cloud
citrus	citrous	a fruit
coccus	coccous	a spherical bacterium
estrus	estrous	heat: female sexual receptivity
fucus	fucous	seaweed
fungus	fungous	mushrooms and other such organisms
hamulus	hamulous	a hook at the end of a bone
lupus	lupous	an inflammatory disease
mucus	mucous	a viscous secretion
pappus	pappous	a bristly projection of a plant
phosphorus	phosphorous	a flammable element
pileus	pileous	a botanical or zoological cap-shaped part
pilus	pilous	a hair
ramus	ramous	a branch
scirrhus	scirrhous	a hardened tumour
stratus	stratous	a layered cloud
torus	torous	a doughnut-shaped object
typhus	typhous	an infectious disease
villus	villous	a hair
vomitus	vomitous	ejecta of the stomach

and, for the sake of completion, though I was going to leave them out:

anestrus anestrous
diestrus diestrous
microvillus microvillous
oestrus oestrous
organophosphorus organophosphorous

(If anybody knows how to get rid of that big wad of empty space up there above the table, please let me know. My HTML is not great, and I don't know why it's there.)

Sometimes there isn't a word where you'd expect there to be one. Why do we have "tarsus" but not "tarsous", and "sulcus" but not "sulcous"? You'd think the medical world could find a use for those. Often English just takes its usual route and makes one word serve for both purposes: "sinus" is both a noun and an adjective without resorting to "sinous".

Here's a pair that isn't: "populus" and "populous". Both words exist, but "populus", though it be a noun, doesn't refer to people but to trees, specifically the poplar (which is related in a way to "populous", but not enough to make this one of our word pairs.)

There is another set of word pairs in which the adjectival form is "-ose" rather than "-ous": "thrombus" and "thrombose", for instance. (Sometimes all three exist: "torous" and "torose" are both adjectives for "torus".) I'm not compiling those. At least not today.