Re Two"s company; three's a crowd.

[I like English]

Dear teachers,

I am writing to ask the following expression.
"Two"s company; three's a crowd." What does this mean?

Thanks!

Emily

[Casiopea]

"Two is company" refers to two people, notably a couple, like boyfriend and girlfriend, or two good friends, or a husband and a wife. If you and your partner/friend want to be alone or do something together, but your friend or a family member is there with you, that makes three of you, and that's too many people, especially if you want to be alone. "Three is a crowd." It's just too crowded.