Einfix

Einfix is a term encountered in a limited number of theoretical discussions in linguistics to denote a form of infixation in which a morpheme is inserted inside the base form rather than at an edge. The term blends the German prefix ein- (often meaning "inside" or "within") with infix, highlighting its internally positioned status. There is no single, widely accepted definition, and einfix is not part of the standard typology of affixation; instead it appears as a descriptive label in discussions of nonconcatenative morphology or morpheme alternants in constructed languages.

Definition and distinction: An einfix is typically described as a morpheme that attaches within a stem, altering the internal structure rather than adding a suffix to the word. This contrasts with standard infixes which replace or modify internal segments in languages such as Tagalog, Malay, or Filipino, and with circumfixes or prefixes that target word edges.

Usage and sources: The concept is mostly scholarly and rare, appearing in a handful of papers or language-design notes. Some authors use einfix to emphasize internal insertion when analyzing morphological processes that seem to behave like infixes but are constrained by the root's morphology.

Examples: In theoretical discussions, a hypothetical einfix might be inserted after the first consonant of a stem to indicate a grammatical category; such examples are constructive and not documented as attested natural-language data.

See also: Infix, Nonconcatenative morphology, Morphology.