The Korean alphabet has 10 vowels and 11 more compound vowels (2 or more vowels put together). The main 10 have actually 4 sounds (ㅏㅓㅗㅜ). Add a "y" sound (and an extra - mark) and you have the corresponding 4 (ㅑㅕㅛㅠ). The last 2 (ㅡㅣ) are bonus. I love the symmetry and logic of the horizontal and vertical lines, don't you?
The transliterations/depictions/romanizations of the Korean vowels are often misleading. For example, the vowel ㅏ is depicted as "a" which could be thought of as "a" as in apple. So when you say, 가자 (let's go) like "ga-ja" you sound like the proverbial American-accented Korean. But if you said it, "gah-jah" then you could possibly sound somewhat more Korean.
Another example, the ㅓ vowel is often depicted as "eo" so 엄마 (mommy) is transliterated as "eomma" but it sounds more like "uhm-ma." To me, "eo" doesn't look like the "uh" sound. As in "uh...what the...?"
And actually, I've discovered most of our vowels have an equivalent sound in our English exclamatory vocabulary. Let me show you:
아 = "ah" as in "Ah! Ha!" or when the doctor puts a stick down your throat, say "ah"
어= "uh" as in "Uh...ok..."
오= "oh" as in "okay" or "OH!!! I didn't know that!"
우 = "oo" as in "oooooo....you're in trouble!! I'm telling!"
으 = "eu" as in "euuu...that's gross" (not EEW) or the "euuuu" that Lucy makes when Ricky learns that she snuck on the set to his show.
이 = "ee" as in when the dentist says to show him your front teeth.
====== Now, add the "y" sound to the first 4 vowels:
야 = "yah"
여 = "yuh"
요 = "yoh"
유 = "yoo"
========Now, all 10, in order:
아 = ah
야 = yah
어 = uh
여 = yuh
오 = oh
요 = yoh
우 = oo
유 = yoo
으 = eu
이 = ee