「会う」 (au) means "to meet." This verb describes encountering someone or something. When meeting a person, the person you meet is usually marked by the particle に (ni). For example, 「友達に会います。」(Tomodachi ni aimasu.) means "I meet my friend."

会(あ)うは人(ひと)と出(で)会(あ)うこと。友(とも)達(だち)に会(あ)います。