Every noun in Spanish has a grammatical gender — masculine or feminine. This affects the articles, adjectives, and pronouns that go with it.

General Rules

• Nouns ending in -o are usually masculine: libro (book), vaso (glass)
• Nouns ending in -a are usually feminine: mesa (table), casa (house)
• Nouns ending in -ción / -sión / -dad are usually feminine: nación, ciudad
• Nouns ending in -ma (Greek origin) are usually masculine: problema, mapa

Common Exceptions

• la mano — the hand (feminine despite -o)
• el día — the day (masculine despite -a)

Making Nouns Plural

• Ending in a vowel: add -s → libro → libros
• Ending in a consonant: add -es → ciudad → ciudades

Pro tip: Don't just learn libro — learn el libro. Memorize gender with the article from day one.