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In social relationships, an ex (plural is exes) is someone with whom a person was once associated, in a relationship, marriage, or once talked to. As a prefix, ex- can refer to a variety of different relationships; for example, one might refer to a music group's ex-guitarist, or someone's ex-friend.
When used alone, ex as a noun is assumed to refer to a former sexual or romantic partner, especially a former spouse. This often has a derogatory tinge, especially if it refers to unrequited feelings.
Video Ex (relationship)
References
Source of the article : Wikipedia