In phonetics and phonology, gemination (/ˌdʒɛmɪˈneɪʃən/; from Latin geminatio 'doubling', itself from gemini 'twins'[1]), or consonant lengthening, is an articulation of a consonant for a longer period of time than that of a singleton consonant.[2] It is distinct from stress. Gemination is represented in many writing systems by a doubled letter and is often perceived as a doubling of the consonant.[3] Some phonological theories use 'doubling' as a synonym for gemination, while others describe two distinct phenomena.[3]
Consonant length is a distinctive feature in certain languages, such as Japanese. Other languages, such as Greek, do not have word-internal phonemic consonant geminates.
Consonant gemination and vowel length are independent in languages like Arabic, Japanese, Finnish and Estonian; however, in languages like Italian, Norwegian, and Swedish, vowel length and consonant length are interdependent. For example, in Norwegian and Swedish, a geminated consonant is always preceded by a short vowel, while an ungeminated consonant is preceded by a long vowel.