「言う」 (iu) means "to say" or "to tell." This verb is used for expressing words or thoughts. What is said often precedes と (to) or you can use を (o) for a direct object. For example, 「『こんにちは』と言います。」("Konnichiwa" to iimasu.) means "I say 'Hello.'"

言(い)うは言(こと)葉(ば)を口(くち)に出(だ)すこと。「こんにちは」と言(い)います。