sinéresis

Sinéresis is a phonological and prosodic process in which two adjacent vowels within a single word are pronounced as one syllable. It is closely related to the broader concept of syneresis and is often discussed together with diéresis or diaeresis, which describes the opposite tendency: two vowels that would form a hiatus are pronounced as two separate syllables.

The term is primarily used in the study of Romance languages and classical poetry, where syllable counts are crucial for meter. Sinéresis can occur as a regular feature of a dialect, or as a stylistic option exploited by poets to fit a metrical scheme. In many traditions it is historical or dialectal rather than universal, and its use can vary across time and region.

In poetry, sinéresis reduces the total number of syllables by merging a vowel pair that could otherwise form two syllables; diéresis, conversely, increases the syllable count by splitting such pairs. The phenomenon has been described under various names in different languages. In Spanish, Catalan and Portuguese prosody, sinéresis is a recognized concept, while in French prosody the related process is commonly treated under the term synerèse; diaresis or diéresis is used orthographically in languages such as French to indicate two syllables when vowels would otherwise fuse.

Orthographic signals often accompany diacritical marks that indicate whether a vowel pair should be pronounced as one syllable or as two. The concept remains a point of reference in historical phonology, poetics, and dialectology, illustrating how vowel sequences influence syllabification and rhythm. See also hiatus, diéresis, synérèse.