Compounding, the combination of free morphemes, is another common way to form words. The over-whelming majority of English compounds are the combination of words from two of the three classes --- nouns, verbs, and adjectives, and they fall into the three classes, as shown below:

　　In compounds, the rightmost morpheme determines the part of speech of the word. Thus greenhouse is a noun, whitewash is a verb. The leftmost morpheme takes the primary stress of the word. Thus, a greenhouse is distinguished from a green house, in which the stress is on the house.

　 The meaning of compounds is not always the sum of meaning of the components. A greenbottle is not a type of bottle; it is a kind of fly. And a sugar-daddy is not a sugar-coated father, but a woman's lover who is both generous and too old for her.