indefinite article
BAD : I had never visited an hospital before.
GOOD : I had never visited a hospital before.
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Before a word beginning with h , use a if the h is pronounced: 'a house', 'a half', 'a horrible day'. Use an if the h is silent: 'an hour', 'an honour'.
If the h is pronounced but the syllable is unstressed, it is possible to use a or an ('a/an hotel'). However, the use of an here is considered old-fashioned and most people use a .