The ordinal form of the number fifty-one, describing a person or thing in position number 51 of a sequence.

One of fifty-one equal parts of a whole.

The ordinal form of the number sixty-one, describing a person or thing in position number 61 of a sequence.

One of sixty-one equal parts of a whole.

A basic, foundational proposition or assumption that cannot be deduced from any other proposition or assumption.

A statement that is not proved but rather supposed or held as obvious, forming together with other such statements the basis of a system of statements obtained from them by inference; an axiom.

Early in the morning. / Straight away, very soon.

The basic idea of how to do something. / Used other than figuratively or idiomatically: see first, thing.

plural of first name

plural of first principle