In linguistic morphology, a disfix is a subtractive morpheme, a morpheme manifest through the subtraction of segments from a root or stem. Although other forms of disfixation exist, the element subtracted is usually the final segment of the stem.
Productive disfixation is extremely rare among the languages of the world but is important in the Muskogean languages of the southeastern United States. Similar subtractive morphs in languages such as French and Portuguese are marginal.
The terms "disfix" and "disfixation" were proposed by Hardy and Timothy Montler in a 1988 paper on the morphology of the Alabama language. The process had been previously described by Leonard Bloomfield who called it a minus feature, and Zellig Harris who called it a "minus morpheme". Other terms for the same or similar processes are subtraction, truncation, deletion, and minus formation.
Bloomfield described the process of disfixation (which he called minus features) through an example from French although most contemporary analyses find this example to be inadequate because the masculine forms might be taken as the base form and the feminine forms simply as suppletives. Though not productive like Muscogean and therefore not true disfixation, some French plurals are analysed as derived from the singular, and many masculine words from the feminine by dropping the final consonant and making some generally predictable changes to the vowel:
Historically, this reflects that the masculine was once pronounced similar to the current feminine, and the feminine formed by adding /ə/. The modern situation results from regular apocope which removed a consonant from the masculine and the final schwa of the feminine.
In Portuguese, some words which have the masculine ending -ão have a feminine equivalent -ã, synchronically analyzable as a disfixation.
irmão - irmã (brother - sister)
cristão - cristã (Christian m. - Christian f.)
bretão - bretã (Breton m. - Breton f.)
artesão - artesão (craftsman - craftswoman)
órfão - órfã (orphan m. - orphan f.)
charlatão - charlatã (conman - conwoman)
The root cause of this disfixation is the loss of intervocalic -n- in the evolution of Latin to Portuguese. Therefore, the Latin ending -anus became -ão in Portuguese and its feminine -ana became -ãa and then -ã. For comparison, notice the Spanish equivalents hermano-hermana, cristiano-cristiana, etc.
It is important to note, however, that not all words with -ão come from Latin -anus, meaning that their feminine derivation will be different (cf. leão-leoa, for instance). There are also words whose disfixation was made by comparison (the case of charlatão, which is a French loanword).
There are also two words which have feminine derivations made through disfixation: mau (bad) and réu (defendant, as used in law), whose feminines are má and ré respectively.