I think love is where you always have that person on your mind. No matter where you are, your looking for them hoping they'd be around somewhere. Even if they hurt you more than anyone ever has, you still want to be with them. Every word they say means everything to you. You don't want to admit it, but everything reminds you of them, and makes you want to cry. I think its love when your favorite smell is his smell. You listen to song after song just cause it reminds you of him. You miss his touch, his kisses, and his smiles, even after he's a complete ass. You sometimes wish he'd call you late at night and talk for hours, like he used to. Stay up late remembering it used to be with him. You look at your phone all day wishing he'd text you. You miss holding his hand and never wanting to let go. You wish you would get those butterflies again, but know that he's the only one who can give them to you.
I think thats when you know you love someone.