Sept or hept
The prefix hepta- means seven. A heptagon is a polygon with seven sides. Other words that have this same prefix are: heptathlon, heptameter, herpetology, heptarch, heptads.
The prefix for inadequate is in-. The prefix in- means not.
The prefix in non-. This prefix means not.
The prefix is poly-. This prefix means many.
The prefix is 'a'. When applied to a word it means 'not'. Hence 'atheist' is NOT believing in a God. ( theist). Other words that 'a' can be applied to are 'apolitical' Not / above politics. 'Asexual' not sexual as applied to single cell life forms.
The prefix in the word "confide" is "con-," which means "with" or "together."
The prefix of "heptathlon" is "hept-" which means seven.
The prefix a- means NOT. In the word amoral it means the opposite of moral.
sept
an- means "not"
The prefix ben- means good.
The prefix in the word maladjusted is mal-. This prefix means bad.