Union - GCSE Maths Definition

In GCSE Mathematics, the term 'union' means 'or' - particularly in relation to probability. The symbol ∪ is used for union. Generally, union is used in set theory - a 'set' of numbers will be a list of numbers that all have a particular property; for example, the set of numbers that are the factors of 12 would be written as {1, 2, 3, 4, 6, 12}.

If, say, set F represents students at a school studying French, and set S represents students at a school studying Spanish, then we could refer to the students studying French or Spanish as F ∪ S. In words, F ∪ S would be "(the set of students studying) French or Spanish or both".

In probability, P(A ∪ B) would be 'the probability of event A happening, or event B happening, or both happening'.