恒星口语讲堂:"约会"用英语怎么说?

如果两个人成为夫妻，或是结成了长期稳定的伴侣关系，又该怎样描述呢：

A couple: two people dating exclusively
例如：They are really nice couple.

An item: a couple who is the topic of gossip or interest.
例如：So are you two an item now?

Sweet heart: girl friend or boyfriend; implies a sweet relationship
例如：He married his high school sweet heart.

Lovers: a couple who show their affection openly
例如：Those two lovers just got married last month.