2 of 3 -4 bytes thanks to @Sunny Pun

Perl, 47 43 + 1 = 44 bytes

-4 bytes thanks to @Sunny Pun

Run with the -n flag.

say!!/^(s(in?)?|co?|t(an?)?|ln?|log?|e)+$/i

I'm not sure this regex can be golfed any further, but I'll keep trying things.

Try it online!

I downloaded a dictionary file, and the longest word I found was 11 letters -- tattletales