A unique is correct. Why "a unique..." rather than "an unique..."? "a" precedes words that begin with Consonant SOUNDs...[Sound not alphabet..I mean] "an" precedes words that begin with Vowel SOUNDs... When a "u" word is pronounced as though it begins with a "y" (yoo nique) /ju:nik/, it's treated more like the consonant sound of the y. So, a university, a usual day, an unusual day, an umbrella, Moreover, "h" alphabet is the same when using an article. e.g. a house , a holiday , an hOur : the "h" in hour is silent, it sounds like the vowels "ou

The first one is right...cuz unique pronunces /ju:/ and /j/ is not the vowel.

HI. I think that 'A unique' is correct. 'An' is used before certain vowel sounds to make them easier to say. 'An unique' is harder to say than 'A unique' so there is no reason to use it. Just say the word with both 'a' and 'an' and decide which is easier to say. I think that 'unique' starts with a 'Y' sound - 'you-neek' when spoken by an english native. So it is not a vowel sound. (Even though it is a vowel). If you take a different example such as: An umbrella. There is a vowel sound so it is easier to say 'An umbrella' than 'A umbrella'. (snownoir makes the point well)

Yes, it's about the sound - not the written convention. "An" is used to make the transit between vowel sounds smoother. Same rule for "H" words: a horse, an hour...

It's "a unique", not "an unique". Jeannie and snownoir explain it well.