In English, as you already know, we usually make nouns plural by adding "s" to the end of the word, unless it ends in "y," in which case the "-y" is dropped and replaced by an "ies." In Spanish, it is almost as simple, and Spanish has few of the numerous and unpredictable exceptions that English has. For the sake of simplicity and clarity, the examples given in this lesson are for nouns, but the same rules apply for adjectives.
The basic rule: The rule that you follow most of the time is roughly the same as the rule in English: If a word ends in a consonant, add -es. If it ends in an unaccented vowel, simply add an -s. In Spanish, y is treated as a consonant for purposes of pluralization.
- Examples: un árbol (one tree), dos árboles (two trees); el actor (the actor), los actores (the actors); el hotel (the hotel), los hoteles (the hotels); un taco (a taco), dos tacos (two tacos); un perro (a dog), tres perros (three dogs); un rey (a king), cuatro reyes (four kings).
Orthographic changes: Some words follow the general rule in terms of pronunciation, but a change in either a letter or an accent mark is needed. In plurals of words that end in -z, the -z changes to -ces for the plural. And if the addition of -es would change which syllable gets the accent, an accent is either dropped or added.
- Examples: el juez (the judge), los jueces (the judges), una vez (once), dos veces (twice), el inglés (the Englishman), los ingleses (the Englishmen), la canción (the song), las canciones (the songs), el examen (the exam), los exámenes (the exams).
Words ending in stressed vowels: Words that end in a stressed -é form the plural simply by adding -s. Words that end in other stressed vowels have an -es added. There are four common exceptions: el papá (the father), los papás (the fathers); una mamá (a mother), dos mamás (two mothers); el dominó (the domino), los dominós (the dominoes); and un sofá (a sofa), tres sofás (three sofas).
- Examples: el rubí (the ruby), los rubíes (the rubies); el hindú (the Hindu), los hindúes (the Hindus); el café (the coffee), los cafés (the coffees).
Finally, the exceptions: The above rules cover probably 99 percent of the nouns you will use. Most of them are words that are identical in the singular and plural — e.g., la crisis (the crisis), las crisis (the crises) — and new words of foreign origin, which often follow the pluralization rules of the originating language — e.g., la tablet Android (the Android tablet), las tablets Android (the Android tablets). As a beginner, the main exceptions you need to know are the days of the week, Monday through Friday, which are the same in singular and plural — los lunes (Mondays), los martes (Tuesdays), and so on.
For a more thorough treatment of the exceptions, see this longer lesson on plurals.