Open vs Closed syllables

Open Syllable and Long vowel pronunciation

Rule: When a stressed syllable ends in a vowel (an open syllable), that vowel is usually pronounced as its long sound (its letter name).

Word Syllable Division Open Syllable Long Vowel IPA
baby ba · by ba A → /eɪ/ /ˈbeɪ.bi/
paper pa · per pa A → /eɪ/ /ˈpeɪ.pɚ/
music mu · sic mu U → /juː/ /ˈmjuː.zɪk/
tiger ti · ger ti I → /aɪ/ /ˈtaɪ.ɡɚ/

The open syllable rule is one of the strongest pronunciation rules in English.