(countable) A number or part of a whole which is greater than any other number or part, but not necessarily a majority.
(countable) A number of votes for a single candidate or position which is greater than the number of votes gained by any other single candidate or position voted for, but which is less than a majority of valid votes cast.
Synonym: relative majority
(countable) A margin by which a number exceeds another number, especially of votes.
https://en.wiktionary.org/wiki/plurality
https://en.wiktionary.org/wiki/majority