The phrase “have in common” is used when you compare people or things. The phrase “have in common” means to share characteristics with. In other words, what is the same about the things you are talking about. For example:

What do Ann and her sister have in common? They both have black hair, they both wear glasses, and they both like shopping.

What do dogs and cats have in common? They are both popular pets in the U.S.

What do Thanksgiving and Christmas have in common? They are both holidays at the end of the year where people meet their families and have a big meal together.

If there are many things the same, we often say, “They have a lot in common.” If nothing is the same, we often say, “They have nothing in common” or “They don’t have anything in common”

My friend and I have a lot in common. We both like scary movies, we both teach at a universities, and neither of us likes hot weather.

My friend’s mother and her daughter have a lot in common.

You and your sister are very different. You don’t have anything in common.

He likes chocolate ice cream; she likes vanilla ice cream. He likes the summer; she likes winter. He likes science; she likes art. Those two have nothing in common.