What does "single" mean in the context of relationships?

[RTFirefly]

@LSLGuy

Occasioned by this thread Would you consider this to be single or not? - In My Humble Opinion - Straight Dope Message Board

I always thought “single” meant “not married at this moment”. Nothing more and nothing less. Ever.

In that thread a lot of Dopers contend that “single” means “not now in any relationship”. So if one dates the same person twice in a row, one is no longer “single”.

Depends on the context. If you’re answering a demographic survey, ‘single’ means you’re not married, and not in a relationship that you regard as the equivalent of being married.

But in most social contexts, ‘single’ = available.