Is holiday uncountable?

[yolanda]

English Grammar Tests, Elementary Level

ESL/EFL Test #98 "Articles in English Grammar", question 3

Please meet me at the train station in ......... hour from now.

(a) a
(b) an
(c) the

English Grammar Tests, Elementary Level

ESL/EFL Test #98 "Articles in English Grammar", answer 3

Please meet me at the train station in an hour from now.

Correct answer: (b) an
_________________________

an hour is correct ,and why an holiday is wrong?

Thank you yolanda

[Conchita]

We can't say 'an holiday' because the article 'an' is used before words beginning with a vowel sound, like 'hour'. Since the 'h' in holiday is pronounced, we say 'a holiday'.