Morphophonology

Morphophonology (also called morphophonemics or morphonology) examines how sound patterns and word-building processes interact. Its central concern is the way morphemes—the smallest units of meaning—change their sound when combined into words. This field sits at the intersection of morphology and phonology.

The study of morphophonology began in the early 20th century with structural linguistics. Key early contributions came from Roman Jakobson on phonological alternations, and later from Chomsky and Halle’s *The Sound Pattern of English* (1968), which formalized the link between phonology and morphology within generative grammar. Subsequent frameworks like Autosegmental phonology and Optimality Theory have further refined how morphophonological patterns are analyzed.

A typical morphophonological analysis produces a set of formal rules or constraints that can predict the regular sound changes affecting a language’s morphemes. These rules convert an abstract underlying representation into a surface form that is actually pronounced. The units in those underlying representations are sometimes called morphophonemes. The surface form may consist of phonemes (which then undergo ordinary phonological rules to become speech sounds, or phones), or the analysis might skip the phoneme stage and generate phones directly.

When morphemes come together, they alter each other’s sound structure (at either the phonetic or phonemic level), creating different pronunciations for the same morpheme. Morphophonology aims to describe these processes. Ideally, a language’s morphophonological rules can predict every such alternation.

For example, the English plural morpheme, written as "-s" or "-es," is pronounced [s], [z], or [ɪz] in *cats*, *dogs*, and *horses*. A purely phonological analysis would assign these three endings the phonemic representations /s/, /z/, /ɪz/. But morphophonologically, they can all be seen as realizations of a single underlying morphophoneme ⫽z⫽, whose surface form depends on the final segment of the morpheme it attaches to. The English past tense "-ed" works similarly, surfacing as /t/, /d/, or /ɪd/ in *hoped*, *bobbed*, and *added*.

The plural suffix can also affect the preceding morpheme. In *leaf* and *knife*, the singular ends in [f], but the plural forms *leaves* and *knives* have [v]. Morphophonologically, these morphemes can be analyzed as ending in a morphophoneme ⫽F⫽ that becomes voiced when a voiced consonant (like the plural’s ⫽z⫽) attaches. This rule can be written using Alpha Notation: /F/ → [αvoice] / __ [αvoice], where α can be + or −.

Morphophonemic representations are often marked with double slashes (⫽ ⫽), consistent with the IPA. Other conventions include pipes (| |), double pipes (‖ ‖), or braces ({ })—the latter from set theory, used when listing phonemes like {s, z, ɪz} for the plural. For instance, *cats* can be transcribed phonetically as [ˈkʰæʔts], phonemically as /ˈkæts/, and morphophonemically as ⫽ˈkætz⫽ if the plural is underlyingly ⫽z⫽, which assimilates to /s/ after a voiceless nonsibilant. The tilde ~ may indicate morphological alternation, as in ⫽ˈniːl ~ nɛl+t⫽ for *kneel~knelt* (the plus sign marks a morpheme boundary).

Inflected and agglutinating languages often have very complex morphophonemic systems. Examples include sandhi (as in the English plural and past tense), found in nearly all languages to some degree—even Mandarin, which has little morphology, displays tone sandhi. Consonant gradation occurs in Uralic languages like Finnish and Estonian. Vowel harmony appears in varying degrees worldwide, notably in Turkic languages. Ablaut, found in English and other Germanic languages, involves stem vowels changing form, as in *sing, sang, sung*.

Until the 1950s, many phonologists assumed that neutralizing rules generally applied before allophonic rules. This split analysis into a morphophonological part (deriving phonemes from morphophonemes) and a purely phonological part (deriving phones from phonemes). Since the 1960s, particularly with the generative school’s work, many linguists have abandoned this division, instead treating the entire process as a single system. Morphophonology continues to evolve, integrating new approaches and deepening our understanding of how sound and word formation interact across languages.