ˈkætəˌɡɔɹi ˈkætɪɡ(ə)ɹi ˈkɛtɘɡ(ɘ)ɹi klɑːs ˈfæm(ɪ)li ˈfæm(ə)li ˈfɛm(ɘ)li a collection of things sharing a common attribute there are two classes of detergents