Originally Posted by Marrez

"an"

you use "an" before a word that starts with a vowel

it doesn't matter that uke's a japanese word, we're using english

a + consonant sound
If the following word starts with a consonant sound, then we say a:

a cat
a game of golf
a human emotion
a Peruvian
a very nice lady

an + vowel sound
If the following word starts with a vowel sound, then we say an:

an apple
an easy job
an interesting film
an old man
an umbrella

The Importance of Sound
Normally, we pronounce consonant letters with a consonant sound, and vowel letters with a vowel sound. But there are some exceptions. The rule about a or an is still the same. You just need to think about the sound, not the writing. Look at these examples:

vowel letter but consonant sound
a European country----------- you-ro-pe-an
a one-day conference ---------- won-day
a university--------------- you-ni-ver-si-ty