“In love” is a mushy concept. People use it to describe everything from a good friendship, to the love of their lives.
I think it’s important to distinguish infatuation from real love. The way I define it, love happens in the context of a working relationship, another word that has a mushy definition, whereas anybody can be infatuated with anybody else.
So let’s define relationships. A relationship is what two people are in when they decide to get, and provide, each other the things they need, exclusively. They are organized around explicit or implicit promises. Cheating is when one partner breaks a promise in order to get a want or a need from someone else.
A need is anything emotional that makes you feel good in a deep way. Safety, friendship, sex, are the main ones that couples often require, and sex is usually the main one that’s promised to be exclusive.
The way I think of love is, if you have found someone that meets all your needs, and there is no question of them breaking their promises to you, because you’ve been in a relationship long enough to tell, then you are in love. It’s something that unfolds slowly over a long period of time spent together.