An infix is an affix inserted inside a stem (an existing word). It contrasts with adfix, a rare term for an affix attached to the outside of a stem, such as a prefix or suffix.
Arabic uses a common infix, ‹ت› ‹t› for Form VIII verbs, usually a reflexive of Form I. It is placed after the first consonant of the root; an epenthetic i- prefix is also added since words cannot begin with a consonant cluster. An example is اجتهد ijtahada "he worked hard", from جهد jahada "he strove". (The words "ijtihad" and "jihad" are nouns derived from these two verbs.)
In Seri some verbs form the plural stem with infixation of ‹tóo› after the first vowel of the root; compare the singular stem ic 'plant (verb)' with the plural stem itóoc. Examples: itíc 'did s/he plant it?' and ititóoc 'did they sow it?'.
Sequences of adfixes (prefixes or suffixes) do not result in infixes: An infix must be internal to a word stem. Thus the word originally, formed by adding the suffix -ly to original, does not turn the suffix -al into an infix. There is simply a sequence of two suffixes, origin-al-ly. In order for -al- to be considered an infix, it would have to have been inserted in the non-existent word *originly. The "infixes" in the tradition of Bantu linguistics are often sequences of prefixes of this type, though there may be debate over specific cases.
The Semitic languages have a form of ablaut (changing the vowels within words, as in English sing, sang, sung, song) which is sometimes called infixation, as the vowels are placed between the consonants of the root. However, this interdigitation of a discontinuous root with a discontinuous affix is more often called transfixation.
See also interfix.
Die akkadischen Verbalstamme mit ta-Infix.(Die akkadischen Verbalstamme mit ta-Infix: Alter Orient und Altes Testament, vol. 303)(Book Review)
Jul 01, 2004; Die akkadischen Verbalstamme mit ta-infix. By MICHAEL P. STRECK. Alter Orient und Altes Testament, vol. 303. Munster:...