It’s a hospital. Since "hospital" begins with a consonant sound (the "h" is sounded), it takes the article "a".
It’s a hospital. We use a or an based on the sound made by the initial letter of the following word—not how it is spelled. Since "hospital" begins with a consonant sound (the "h" is sounded), it takes the article "a".
She will stay in a hospital ward.
She will stay in an hospital ward.
Borrowed from the French, the word hospital had a silent "h"; today, however, not pronouncing it is considered wrong.
You just need to be in a hospital.
She arrived at a hospital in an emergency situation.
Source: Google Books Ngram Viewer
A partial list of words that also start with a sounded "h", and therefore take the article "a":
