It’s a host. The rule for using "a" or "an" is based on pronunciation, not spelling. Since the initial letter (h) of the word host is clearly pronounced, we use the article "a".

It’s a hospital. Since "hospital" begins with a consonant sound (the "h" is sounded), it takes the article "a".

It’s a helicopter. The word helicopter starts with a sounded "h", and therefore takes the article "a".

It’s a habit. The rule for using "a" or "an" is based on pronunciation, and not spelling. Since the word habit starts with a sounded "h", it takes the indefinite article "a".

It’s an hourglass. The word hourglass begins with a silent "h", so it takes the article "an".

It’s an hourly. Choosing between "a" or "an" is determined by the initial sound of the following word. "Hourly" starts with a silent "h" (it sounds like "ourly"), so it takes the article "an".

It’s an hour. Because the word "hour" begins with a silent "h" ("hour" and "our" have the same pronunciation), we use the article "an".

It’s an honorarium. The rule for using "a" or "an" is based on the initial sound of the following word, and not how it is spelled. Since the word "honorarium" begins with a vowel sound (the "h" is silent), we use the article "an".

It’s an honorable. The choice between "a" and "an" is determined by the initial sound of the following word. Since "honorable" starts with a vowel sound (the "h" is silent), it takes the indefinite article "an".