A distinguishing feature of a person or thing.
For a given field or ring, a natural number that is either the smallest positive number n such that n instances of the multiplicative identity (1) summed together yield the additive identity (0) or, if no such number exists, the number 0.
The integer part of a logarithm.
The distinguishing features of a navigational light on a lighthouse etc by which it can be identified (colour, pattern of flashes etc.).
Being a distinguishing feature of a person or thing.
The state of being singular, distinct, peculiar, uncommon or unusual.
An unusual action or behaviour.
A point where all parallel lines meet.
Celibacy, singleness (as contrasted with marriage).
A point where a measured variable reaches unmeasurable or infinite value.
The value or range of values of a function for which a derivative does not exist.