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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.



English has almost no true infixes (as opposed to tmesis, see below), and those it does have are marginal. A few are heard in colloquial speech, and a couple more are found in technical terminology.


  • Chemical nomenclature includes the infixes ‹pe›, signifying complete hydrogenation (from piperidine), and ‹et› (from ethyl), signifying the ethyl radical C2H5. Thus from the existing word picoline is derived pipecoline, and from lutidine is derived lupetidine; from phenidine and xanthoxylin are derived phenetidine and xanthoxyletin.


None of the following are recognized in standard English.

  • The infix ‹iz› or ‹izn› is characteristic of hip-hop slang, for example hizouse for house and shiznit for shit. Infixes also occur in some language games.
  • "Fucking" is sometimes used as an expletive infix, as in "un-fucking-believable". This can also be considered an instance of tmesis.
  • The ‹ma› infix, whose location in the word is described in Yu (2004), gives a word an ironic pseudo-sophistication, as in sophistimacated, saxomaphone, and edumacation.

Other languages

Indo-European languages

The present tense of some Latin and Ancient Greek verbs adds an infixed nasal (m, or n; μ, ν, or γ) to the basic root; the stems of the other tenses use the root without the infix. Latin tang-ō 'I touch' has the perfect stem te-tig-ī 'I touched, have touched' (-tig- weakened from original -tag-) and the perfect passive participial stem tac-tus 'touched' (derived by assimilation from *tag-tus). Greek λαμβ-άν-ω (lambánō; with suffixed -άν-) 'I take' has the aorist ἔ-λᾰβ-ον (élǎbon) 'I took'.

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