How did double consonants function in Classical Latin?

In Classical Latin, double consonants functioned as geminates, which are sequences of identical speech sounds pronounced as a pair. Unlike in many modern English words where doubled letters often serve to indicate vowel length or are pronounced as a single sound, Latin geminates involved the repetition of the consonant sound back-to-back.12

This system of maintaining a distinction between single and doubled consonants was a core feature of the Latin phonological system. While some later Romance languages simplified these geminates—particularly in dialects to the north and west of the La Spezia–Rimini line in Italy—southern and eastern dialects tended to retain the original Latin voiced-voiceless-geminate system. The term itself is derived from the Latin word geminus, meaning "twin," reflecting the nature of these doubled articulations.321