moon – la luna
(Pronounced loo-nah)
To remember that moon is pronounced loo-nah (luna) in Spanish, use the following mnemonic:
He swore the moon was talking to him - his friends thought he was a lunatic (luna).

Luna is feminine, so it's la luna. Imagine that the man in the moon is really a lady:

Examples of luna (moon) in a sentence
La luna llena ilumina el cielo esta noche.
(The full moon lights up the sky tonight.)
Me gusta caminar bajo la luna en verano.
(I love walking under the moon in summer.)
La luna estaba escondida detrás de las nubes.
(The moon was hidden behind the clouds.)