Yes, “folk” is singular. It doesn’t refer to a single person, but to a single group of people. For instance, I might say that the Irish are a fun-loving folk, or I might say that the Irish and the Dutch are fun-loving folks. It’s one of those collective nouns I mentioned earlier.
OK, but that’s a different usage than what I was originally thinking of. When I talk about my folks, I mean my parents. But if I’m just talking about one of them, I can’t refer to him/her as my folk.
Name’s not ed, but nice ta meetcha anyways, connery…er…conman…whatever…
Is smegma singular or plural or does it even matter? Wait, I can answer that last part…
Congratulations
An opposing thought…
There’s no plural for Phoenix.
b-dum - tish!
Fish can be a plural, but fishes is also a plural, and it is used when you have various species of fish together, or is that “various species of fishes”?
Scissors.
In Texas I understand there is “y’all” of which the plural is remarkably “all y’all”.
I’ll now return to my hole…
I’m single. 
FWIW, I live with the word “data” on a daily basis and am surrounded by its use. In my experience it is treated as a plural. And I see and hear the singular “datum” used as well. I will note, though, that my dictionary has a parenthetical note: (often construed as singular).
Phoenices.
Also, the plural of sphinx is sphinges.
Let me guess. Are you a scientist?
Seeing as how the “s” is silent, I think that is a singular noun.
Thanks for missing the point.
By definition, there is only one of the mythical bird Phoenix. Now if somebody goes and names a car or something “Phoenix”…
If the plural of index is indices, does that make the plural of ibex ibices?
Here’s a for–real weird plural. I used to think that he plural of octopus was “octopi”, until someone who actually worked with the eight-tentacled beasts told me the plural is really “octopodes” or “octopuses”. I looked t up in the Oxford English dictionary, and it’s true. "octopus isn’t second declension, but fourth declension irregular.
In a similar vein, a friend tried to stump me by asking the plural of “opus”. Again, it isn’t wha you’d think (“opi”?). But I new the right answer this time – it’s “opera”. And now you know where THAT came from.
Opus/opera…that one will stay with me; that was good, Cal, thanks.
Here’s another stumper:
The word “wrought” is past tense of another English word. Which one?
And one that’s (hopefully) a bit easier: what’s the present tense of “sought”?
I’m (educated) guessing wreak and seek.
Oh, and while we’re off the subject…
When you say “It is raining,” what noun does the pronoun “it” replace?