Korean has two standalone diphthongs:
oe ㅚ like 'whe' in "when"
In addition, most vowels can be modified by prefixing them with 'y' or 'w':
wa ㅘ wae ㅙ wo ㅝ wi ㅟ we ㅞ ya ㅑ yo ㅛ yeo (yŏ) ㅕ yu ㅠ
