From these examples, we can make a broad distinction between two types of morphemes. There are free morphemes, that is, morphemes that can stand by themselves as single words, for example, open and tour. There are also bound morphemes, which are those forms that cannot normally stand alone and are typically attached to another form, exemplified as re-, -ist, -ed, -s. These forms were described in Chapter 5 as affixes. So, we can say that all affixes (prefixes and suffixes) in English are bound morphemes. The free morphemes can generally be identified as the set of separate English word forms such as basic nouns, adjectives, verbs, etc. When they are used with bound morphemes attached, the basic word forms are technically known as stems. For example:

We should note that this type of description is a partial simplification of the morphological facts of English. There are a number of English words in which the element treated as the stem is not, in fact, a free morpheme. In words such as receive, reduce and repeat, we can identify the bound morpheme re- at the beginning, but the elements -ceive, -duce and -peat are not separate word forms and hence cannot be free morphemes. These types of forms are sometimes described as “bound stems” to keep them distinct from “free stems” such as dress and care.