Lacking something essential; often construed with in.
Insufficient or inadequate in amount.
Of a number n, Having the sum of divisors σ(n)<2n, or, equivalently, the sum of proper divisors (or aliquot sum) s(n).
A person who is deficient.
Certain in one's knowledge or belief.
Physically secure and certain, non-failing, reliable.
Certain to act or be a specified way.
Yes, expressing noncommittal agreement or consent.
Yes; of course.
You're welcome; polite response to being thanked.
Without doubt, certainly.