Semivowel
Semivowels are consonants that almost sound like vowels. In English, the semivowels are written as W and Y (written as /w/ and /j/ in IPA). In Latin, even though semivowels are phonemes, or unique sounds, they have no special letters used to write them. The letters V and I were used to write the sounds /w/ and /j/, and these same letters were also used to write the vowels /u/ and /i/ in the same order. For example, Gaius Julius Caesar was written as Gaivs Ivlivs Caesar and wine was written as vinvm. The letter J was added after the fall of the Roman Empire to write the semivowel /j/ to show the difference between /j/ and /i/.