…'sThis combines two small endings that attach directly to a word for a person: たち (tachi) turns that person into a group, and の (no) works like "'s" in English to show that something belongs to them. Because Japanese builds words this way instead of switching to completely different words like "our" or "their", you just attach たちの (tachi no) right to the end of the person word. For example, 私 (watashi) means "I", so 私たちの先生 (watashi-tachi no sensei) means "our teacher", and 子供たちの本 (kodomo-tachi no hon) means "the children's book".