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.
A distinguishing feature of a person or thing.
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.
An infinitely small quantity which is assumed to admit of no further division.
That which cannot be divided or split.
Incapable of being divided; atomic.
Incapable of being divided by a specific integer without leaving a remainder.