When a syllable ends in /i:/ or /ɪ/ and is followed by by a vowel, most speakers introduce a linking /j/. When a syllable ends in /u:/ or /ʊ/ followed by a vowel, most speakers introduce a linking /w/. These linking sounds are not obligatory (indeed, most speakers are not aware that they use them), and are not normally noted in phonemic transcriptions. They are noted in phonetic transcription.