Learn Spanish (Latin America): Hay un reloj negro y un espejo grande. - There is a black clock and a large mirror.

The word hay is very special because it means both 'there is' and 'there are'. It never changes its shape, whether you are talking about one single item or many items.

Why do negro and grande come after the words they describe?

In Spanish, descriptive words usually come right after the noun they describe. That is why we say reloj negro (clock black) and espejo grande (mirror big) instead of putting the describing word first like in English.

Why doesn't grande end in -o to match the masculine word espejo?

Descriptive words that end in the letter -e, like grande, do not change to match gender. You use the exact same word for masculine nouns like espejo and feminine nouns like mesa.

Does reloj mean 'clock' or 'watch'?

The word reloj is used for both 'clock' and 'watch' in Spanish. You can usually tell which one the speaker means based on the situation.