Definition

1. Noun:
   • A variant phonological form of a morpheme: An "allomorph" is one of the different phonetic or phonological realizations that a single morpheme (the smallest meaningful unit in a language) can take, depending on its phonetic environment.
   • A variant crystalline form of a chemical compound: In geology and chemistry, an "allomorph" refers to one of the different possible crystalline structures that a single chemical substance can assume.

Usage Examples

• Linguistics (Morpheme Variant): The phonemes /s/, /z/, and /ɪz/ are allomorphs of the English plural morpheme, as in 'cats', 'dogs', and 'horses'. In the past tense, the morpheme '-ed' has allomorphs like /t/ in 'walked', /d/ in 'played', and /ɪd/ in 'wanted'.

• Science (Crystalline Form): Calcium carbonate has the allomorphs calcite and aragonite, which have different crystal structures. Diamond and graphite are allomorphs of the element carbon.

Advanced Usage

• Conditioned vs. Free Variation: In linguistics, allomorphs can be in complementary distribution (each form appears in a specific, predictable phonetic context, like the plural /s/ after voiceless sounds) or in free variation (where forms are interchangeable, though this is rarer for grammatical morphemes).
• Polymorphism: In materials science, the phenomenon of a substance having multiple allomorphs is called polymorphism.

Variants and Related Words

• Allomorphic (adj): Relating to or characteristic of allomorphs.
• Morpheme (n): The smallest grammatical unit of meaning (e.g., 'un-', 'happy', '-ness' in 'unhappiness').
• Allophone (n): A linguistics term for a variant phonetic form of a single phoneme (a sound unit), not to be confused with "allomorph," which is a variant of a meaning unit.

Synonyms

• Variant form: A more general term for any alternate shape or manifestation.
• Alternant: A term sometimes used in linguistics for a variant form of a morpheme.
• Polymorph: In science, a synonym for a substance existing in multiple crystalline forms.

Notes on Meaning

• The two primary meanings of "allomorph" belong to completely different fields (linguistics and mineralogy/chemistry). The intended meaning is always clear from the academic or technical context.
• The core concept linking both definitions is that of a single underlying entity manifesting in different observable forms based on specific conditions.

Noun

1. a variant phonological representation of a morpheme
   • the final sounds of `bets' and `beds' and `horses' and `oxen' are allomorphs of the English plural morpheme
2. any of several different crystalline forms of the same chemical compound
   • calcium carbonate occurs in the allomorphs calcite and aragonite