Learn French: Il est un homme.

In French, all nouns have a gender (masculine or feminine). The word for man, homme, is masculine, so it takes the masculine word for "a" or "an", which is un. If we were talking about a woman (femme), we would use the feminine word une.

Why does un homme sound like "uh-nom" when spoken?

The letter "h" at the beginning of homme is silent. Because un ends in a consonant and the next spoken sound is a vowel (the "o" in homme), the words link together. This linking is called a liaison. You pronounce the "n" from un right into the start of homme.

Does un mean "a" or the number "one"?

It means both! In French, un (masculine) and une (feminine) act as the words "a" or "an", but they are also the number "one". Here it translates best to "a man", but it could also mean "one man" if you were counting.

I have seen people say C'est un homme to mean "He is a man". Which one is right?