Atypical means not customary or usual. She had an atypical accent for a Bostonian.

Basically, the most effective approach is to try to identify the type of depression, whether typical, or atypical, (chromium deficiency?

The Greek prefix "a-" in "atypical" means "not" or "without," so "atypical" means not typical or not conforming to the usual pattern.

I was drawn to her atypical style; she always wore vibrant colors and bold patterns.

The letter 'a-' is the prefix in atypical.