Your task is to choose a certain two-letter word, such that when added to each of the listed below words a new valid English word will be created.
You can add your word as a prefix, a suffix or insert within the given word.

abled
aspire
cave
comb
conus
creed
form
lest
lion
one
pent
there

1. All new words must appear in a respectable dictionary.
2. For the less-common words please provide a short definition.