Union

accouplement

(sexual intercourse)

connexion

(joint)

copulation

(sexual intercourse)

fornication

(sexual intercourse)

groupement

(that which is united; something formed by a combination of parts or members)

mariage

(marriage)

réunion

(in set theory)

union

(the act of uniting or the state of being united)

union

(computing: certain data structure)