Korean has a very well-organized alphabet. To change an a sound to a ya sound, and o to yo (and so on), you just add one extra small line to the vowel, as shown below:

This vowel	sounds like:	With one extra line	it sounds like:
	a in father		ya in yacht
	o in home		yo in yolk
	long u in sue		English word you, and is Romanized as yu
And one new vowel with its y-counterpart:
	aw in lawn, and is Romanized as eo		yaw in yawn, and is Romanized as yeo

This wraps up the simple vowels except for two...