Falling in love
catch someone's eye = to be attractive to someone
Example: "The shy man at the back of the class caught my eye."
to fancy someone (British English) = to find someone attractive
Example: "My friend fancies you!"
to have a crush on someone = to only be able to think about one person
Example: "When I was at school, I had a crush on a film star."
to have a soft spot for someone = to have a weakness for someone
Example: "She has a soft spot for Richard - he can do anything!"
to have the hots for someone = to find someone very attractive
Example: "She's got the hots for the new office manager."
to go out with someone (British English) = to date someone
Example: "They've been going out together for years!"
to go steady = to go out with someone
Example: "They've been going steady since their first year at university."
to fall for someone = to fall in love
Example: "He always falls for the wrong types!"
to fall head over heels for someone = to completely fall in love
Example: "He fell head over heels for her."
to be lovey-dovey = for a couple to show everyone how much they are in love
Example: "They're so lovey-dovey, always whispering to each other and looking into each other's eyes."
to have eyes only for = to be attracted to one person only
Example: "He's dropped all his old friends, now that he has eyes only for Susie."
to be the apple of someone's eye = to be loved by someone, normally an older relative
Example: "She's the apple of her father's eye."
to be smitten by someone = to be in love with someone
Example: "I first met him at a party and from that evening on, I was smitten."
a love-nest = the place where two lovers live
Example: "They made a love-nest in the old basement flat."
to be loved-up (British English) = to exist in a warm feeling of love
Example: "They are one loved-up couple!"
to be the love of someone's life = to be loved by a person
Example: "He has always been the love of her life."
to speak with him english 
