for no particular reason

ape
bonobo
chilly
drill
effortless
feckless
giant
heinous
jocular
kudo
loquacious
mentation
nocturnal
obstreperous
philately
quorum
remonstrate
subterranean
titular
unguent
vellum
waxen
xanthoma
yowl
zephyr

----

1) Which of these words do you think isn't a word?

2) What's the pattern used to generate these words?

3) Which one did I miss in the pattern?

Welcome to the Adult SAT! Silly brain-teasers to poke your Abdulla Oblongata, or whatever it's called. Your brain may thank you later. Or not. If not, I prescribe wine. Then maybe you'll forget you ever started to think about this, and rest easy.

Tiff out.