When you accidentally brush hands or shoulders or thighs.
When you tease each other like little kids.
When someone says a song or show or meme reminded them of you.
When you continuously make eye contact with each other from across the room.
When you notice someone checking you out.
When you get playfully competitive with each other.
When your hug lingers for a little too long.
When you swap sexual jokes and innuendos.
When you share a straw to a drink or a spoonful of dessert.
When you wittily banter back and forth with each other.
When you share silence that is filled with sexual tension.
When you send each other good morning messages.