Protophonology

Protophonology is a term in linguistics describing the earliest stage of a language's sound system, before stable phonemes and phonological rules emerge.

The concept is used in two domains: child language acquisition and historical and comparative linguistics.

In acquisition, protophonology covers pre-phonemic vocalizations such as babbling, which precede a defined phoneme inventory. Children explore broad articulatory gestures and simple syllable shapes, with small or limited inventories and general phonotactic tendencies that later give rise to contrastive sounds.

In historical linguistics, protophonology denotes a pre-phonemic stage in proto-languages where sounds are not yet distinct phonemes but exist as allophones, gestural realizations, or context-bound pronunciations. Regular sound correspondences and gradual mergers then produce a stable phoneme inventory and systematic phonology.

Note that the term is not universally standardized; some authors use pre-phonology or protolanguage instead.