연애 관련.

연애 한지 얼마나 되셨었어요?

How long have you been going out together?

How long have you been dating?

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연애 자체를 명사로 사용하려면..

결혼을 전제로 하면 courtship

courtship is undertaken only when both parties are prepared to make a commitment to marriage.

결혼을 전제로 하지 않으면 dating이라고 하면 될듯.

Men and women who choose to date often have no commitment to consider marrying the other person. 

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the ​time when ​people have a ​romantic ​relationship with the ​intention of getting ​married:They had a ​passionate courtship and a ​long, ​loving ​marriage.
 the ​period in which two ​people have a ​romantic ​relationship that often ​leads to ​marriage:[C] They were ​married in 1923 after a ​long courtship.
[그들은 긴 연애 후에 1923년도에 결혼했다.]