Formative

A formative is a exponent of a morpheme. Formatives comprise not anly affixes, phrasal affixes and particles but also non-concatenative changes like umlaut, tone or stress change, deletion of one or more segments, consonant mutation and the like.

The term became well-known in the 1960s through its use in Chomsky & Halle (1968).

Examples
English plural morpheme is the formative -s like in cat-s (cat+PL).

One of the German plural morphemes consist of the formative -e plus the umlaut of the stem vowel like in Stühl-e (Stuhl+PL) ‘chairs’. (Such morphemes are called simulfixes.)

A circumfix can be seen as consisting of two formatives: a prefix and a suffix.

The German clause negation particle nicht is a formative. Despite its syntactical separation from V0 grammatically (morphologically) it is a part of the verb inflection.

Subtypes

 * Affix
 * Particle

Origin
The term formative was introduced by Karl Brugmann (see Brugmann 1908), as a replacement for suffix, which he thought had unwanted diachronic connotations (Latin suffixum originally means 'attached element' and might suggest that such an element arose from a previously free word by diachronic aglutination).

other languages
German Formativ