Learn Spanish (Latin America): ¡Feliz cumpleaños, abuela!

While you absolutely can say ¡Que tengas un feliz cumpleaños! (I hope you have a happy birthday) using the subjunctive, ¡Feliz cumpleaños! is a fixed, standalone greeting. Just like in English, we usually use the shorter version for standard celebrations rather than spelling out the whole verb phrase.

Why does cumpleaños end in an -s? Is it plural?

It's a compound word that literally means "completes years"! It combines the verb cumple (from cumplir, meaning to turn an age or complete) and the plural noun años (years). Even when talking about a single birthday, the word always keeps that -s at the end.

Does the adjective feliz change depending on the gender of the noun?

No, because feliz ends in a consonant (-z), it has the same form for masculine and feminine nouns. However, if the noun is plural, it does change! You swap the -z for a -c and add -es, making it felices, like in ¡Felices fiestas! (Happy Holidays!).

Could I say abuelita instead of abuela here?

Yes, absolutely! Abuela is perfectly natural and polite, but adding the diminutive ending -ita to make abuelita is very common in Latin America. It's used as an affectionate term of endearment, similar to "granny" or "grandma" in English.