union

A union is the organisation workers join so they can bargain with the boss together instead of one at a time. The teachers' union voting on a strike, a union rep sitting beside you in a disciplinary meeting, union dues coming out of your pay.

The full British name is trade union; Americans say labor union. Under that job sits the plain meaning: a union is the joining of two things into one. Countries use it about themselves — the European Union, the Soviet Union, and in the American Civil War the Union meant the northern states. It also names a marriage or a long partnership in formal writing: their union lasted forty years. In maths, the union of two sets is everything in either of them. One spelling note: it takes a, not an, because it starts with a y sound.