Signs that may indicate attraction
Reciprocal flirting, initiating one-on-one time, sexual humor, physical closeness and discussing casual dating can all indicate possible interest. None of them alone establishes consent or an FWB preference.
Why “signs” are easy to overread
Friends can be affectionate, flirtatious or curious without wanting sex. Someone can also want sex without wanting an ongoing FWB relationship. The interpretation changes with context.
The difference between attraction and agreement
Attraction answers “might this person be interested in me?” An FWB conversation answers “do we both want this kind of relationship?” Those are different questions.
How to find out
Once there is enough mutual comfort, ask. A respectful direct question is more reliable than trying to convert ambiguous behavior into certainty.
A practical pre-start check
Ask yourself three things before raising the idea. First, would you genuinely accept a no without trying to wear the person down? Second, are you being honest about wanting something casual rather than quietly treating FWB as a stepping stone to commitment? Third, are you prepared to discuss sexual health and boundaries as directly as you discuss attraction? If the answer to any of those is no, slowing down is more useful than finding a cleverer line.
Clarity should make opting out easy
A strong beginning is not measured by whether the other person agrees. It is measured by whether they understand what is being proposed and can choose freely. That makes the arrangement more informative for both people: a yes means more, and a no can be respected without turning the friendship into a negotiation.
Labels help describe a relationship, but expectations are specific to the people in it. When something important changes, a direct conversation is usually more useful than trying to decode a rule from the internet.