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.
An exception, or something having an exceptional value
Corresponding to something of lower dimension under a birational correspondence.
Forming an exception; not ordinary; uncommon; rare.
Better than the average; superior due to exception or rarity.