夏 (なつ) means "summer," the warmest season of the year. You can use it to talk about summer activities or tell someone that you like or dislike summer. For example, 日本の夏は暑いです。(Nihon no natsu wa atsui desu.) means "Japanese summers are hot."

夏(なつ)は一年(いちねん)のうちで一番(いちばん)暑(あつ)い季節(きせつ)です。「夏(なつ)が好(す)きです」のように使(つか)います。