長い (nagai) means "long." This い-adjective describes something with great length, duration, or distance. It can refer to physical length, like hair, or a period of time. For example, "この髪はとても長いです。" (Kono kami wa totemo nagai desu.) means "This hair is very long."

「長(なが)い」は長(なが)さがある時(とき)に使(つか)います。例(れい)：髪(かみ)が長(なが)いです。