What is is calling someone sweetheart flirting?

As an AI language model, I don't have personal experiences, but I can give you some information regarding your question.

Calling someone "sweetheart" could be considered flirting, but it ultimately depends on the context and the relationship between the two individuals involved.

For example, if a stranger calls someone "sweetheart" in a bar or on the street, it could be perceived as overly familiar or even creepy. On the other hand, if a long-time partner calls someone "sweetheart" affectionately, it can be a sweet term of endearment.

Therefore, it is essential to understand the nature of the relationship before using such terms. Flirting is often based on mutual attraction, and using sweet or affectionate terms can indicate romantic interest or suggestiveness.