One of the most common morphological processes, affixation involves the attachment of morphemes to a stem. There are several types of affixes, classified in terms of where they attach to a stem: beginning, end, middle, or around. Prefixes attach to the beginning of a stem. For example, the morpheme un- attaches to stems in such words as unbelievable or unkind. Suffixes attach to the end of stems, such as the plural morpheme –(e)s in English: languages, bushes. Turkish uses the plural morpheme –lar: kitap ‘book’ kitaplar ‘books.’
Affixation is used in many languages to mark inflections on verbs. Spanish marks verbs for person with a suffix:
Hablar ‘to speak’ hablo ‘I speak’ hablas ‘you (singular) speak’ habla ‘he/she speaks’
Swahili, on the other hand, uses a series of prefixes to mark person, tense, and object of a verb:
Verbal prefixes in Swahili: a- ta- ni- penda he-FUT-me-like ‘He will like me’
Only prefixation and suffixation are found in English, but other languages display additional affixation processes. These include infixes, in which case a morpheme is inserted within another stem morpheme rather than at the word edge. The following examples from Leti (Blevins 1999) provide an example:
Nominalizing -ni- in Leti kaati ‘to carve’ k-ni-aati ‘carving’ kasi ‘to dig’ k-ni-asi ‘act of digging’ kakri ‘to cry’ k-ni-akri ‘act of crying’
Finally, a circumfix is a morpheme with two parts, one that attaches to the beginning of the word/stem, and one to the end. A common example is the past tense in German, which is formed by affixing a verbal root with ge- and –t. Thus lachen (laugh) becomes gelacht (laughed). Circumfixation can also be seen the simultaneous prefixation and suffixation.