「中」(naka) means "inside," "middle," or "center." It refers to a position contained within something. For example, if you put something inside a box, you'd say, "箱の中に" (hako no naka ni), meaning "inside the box."

「中」(ちゅう)は「内部」(ないぶ)や「真ん中」(まんなか)という意(い)味(み)です。物(もの)の内部(ないぶ)を示(しめ)します。例(れい)：「箱」(はこ)の中(なか)。」