 Affixes are morphs that can be used only when added to other morphs, thus affixes are bound morphs. They are generally classified into four types depending on their position with reference to the base. Here are some present-day English base forms, the verb play, the adjective kind, and the noun which. Prefixes are affixes preceding the base, for example re as in replay, un as in unkind, or b as in be which. Suffixes by contrast follow the base. Here are some examples from present-day English again. Er as in player, ly as in kindly, or the plural is as in which is. Both prefixes and suffixes are common in present-day English. Infixes are affixes which occur within the base. They are common in the Afroasiatic or the Austronesian languages, as here in Indonesian where karya becomes kinarya. But even contemporary English allows infixation. In expressive language, expletives may be inserted into existing words. I better not pronounce this example, but you know what effing stands for, don't you? Finally, circumfixes circumvent the base. Whereas English does not have circumfixes, they exist in other languages. For example in German verb forms such as ge spilt. Affixes are limited in number in a language. The morphological operation which attaches an affix to another morph is referred to as affixation, or more generally as concatenation.