How do you realize that you are falling in love with a friend?

Perhaps when you realize someone you have been friends with for a long time is a bit different now, you want more. Perhaps there is a tinge of jealousy if they talk with someone else for an extended period of time. Perhaps there are sexual feelings toward them. It is not necessarily bad and could be a good thing but one has to be careful about its impact on the friendship if one party is not interested in more than being friends. Probably worth having an honest conversation without setting expectations ahead of time. That is just my take.