Not much useful information today, class, but interesting, I think. I see the term thematic vowel more in Greek than in English, but you should get the idea. I suppose you should see the comic first:
That “o” in front of “nym” in each of those words is the thematic vowel. It’s what you get when you put two root words together to make a compound. Sometimes the two adjacent vowels combine to something else.
“-nym” is from “onoma,” and it means name. So you have that “o” sitting there.
“syn-” is from “sun” (pronounced “soon”) and it means with. No vowel, so you get the “o” for the thematic vowel.
“ant-” is from “anti” and it means against. “o” is stronger than “i” so you end up with “o” for the thematic vowel.
“pseud-” is from “pseudos,” and it means false. Two “o’s,” so they combine to an “o.”
Now let’s throw you a curve.
We have the word antipasto. “Against pasta,” right? Nope! That “anti” used to be “ante,” meaning before. Over the years, that “e” in Latin changed to “i” in Italian. In Latin, “I love you” is “te amo,” but in Italian you say “ti amo.” So antipasto refers to a course that comes before the noodles.
You don’t need to know much about thematic vowels to write well, but use your spell checker just in case.