to be smitten with someone – to be completely captivated by someone
E.g. Joe is completely smitten with his new neighbor. He can barely talk when she is around.
Gianna can’t stop talking about her new boyfriend – she is totally smitten with him.
to take one’s breath away – when you have such attraction towards someone that you almost find it difficult to breathe
E.g. When I saw my fiancée walking down the aisle, she took my breath away.
Jane takes his new boyfriend’s breath away every time he sees her.
to have a crush on someone – to have romantic feelings for someone
E.g. Steve had a crush on Ava for years before he built up the courage to ask her out.
I have such a crush on the lead actor in this new show! He is so handsome.
to hit it off: to instantly get along well with a person from the first meeting
E.g. Bill and Teri hit it off from the beginning and have been together for a decade now.
I hope you hit it off with your blind date tonight! He is a really nice guy!
to be lovey-dovey: to express love in public by kissing, hugging and touching
E.g. It’s good to see how much in love they are! They’re so lovey-dovey, it makes others jealous.
She is very lovey-dovey with Joey but sometime this makes him feel uncomfortable.
to pop the question: to ask somebody to marry you
E.g. When do you think James is going to pop the question to Maria? She can’t wait to get married.
Congratulations! I’ve heard that Mark popped the question last night. Let me see the ring!
to tie the knot: to get married
E.g. When are you and Steve going to tie the knot? – This year, but we haven’t set a date yet.
We tied a knot when we were in our early twenties and we have been happily married ever since.