This is the 1045th most frequent Japanese word.
合う
"合う" means "to match, to fit, to suit, or to harmonize."
合う is used here to denote matching or agreement between opinions.
友達と意見が合うことは重要です。
It is important to agree on opinions with friends.
合う is used here to indicate a fit or match between the shoes and the feet.
この靴は私の足にぴったり合う。
These shoes perfectly match my feet.
合う is used here to imply compatibility between personalities.