If a noun ends in an unstressed vowel (or in a stressed “e”), simply add “s” to the end of the word to make it plural.
el cuaderno becomes los cuadernos
la pluma becomes las plumas
la calle becomes las calles
If a noun ends in a consonant (or in a stressed “a”, “i”, “o”, or “u”), simply add “es” to the end of the word to make it plural. However if the ending is “s” or “x” and the last syllable is not stressed, “es” is not added.
la ciudad becomes las ciudades
la canción becomes las canciones [notice how the accent was dropped]
el oasis becomes los oasis
When a noun ends in “z”, the “z” changes to “c” when the noun is made plural.
| root | la raíz -> las raíces |