In Portuguese, plural forms of nouns and adjectives (o plural dos substantives e adjectivos) are built according to these rules:
In general, especially if the word has an ending vowel then append “s”:
- a menina (the young girl) –> as meninas
- o menino (the young boy) –> os meninos
Examples: A menina e os meninos gostam de canetas alemãs (The girl and the boys like German pens).
Stressed aõ usually becomes ões:
- a lição (the lesson)–> as lições
Examples: As lições duram 45 minutos (the lessons are three quarter of an hour). Minhas mãos são pequenas (my hands are small).
If the word ends in r, s, or z then append “es”:
- o elevador (elevator) –> os elevadores
- o Portuguese (Portuguese, masculine) –> os Portugueses
- a vez (time(s)) –> as vezes
Example: Às vezes e quando (sometimes) os Portugueses usam o elevador (The Portuguese [people] sometimes use the elevator).
If the word ends in m then change its ending to ns:
Example: Os carros são muito bons (the cars are very good).
If the word ends in al the plural becomes ais:
Example: Quais são as coisas mais importantes na vida (which are the most important things in life)?
If the word ends in ol the plural becomes óis:
- o anzol (fishhook) –> anzóis
If the word ends in ul the plural becomes uis:
Example: Canetas azuis (blue pens).
If the word ends in el the plural becomes éis:
- o anel (ring) –> os anéis
If the word’s ending is unstressed il or el the plural becomes eis:
- amável (lovely) –> amáveis
Example: As lições são fáceis e a professora é amável (the lessons are easy and the teacher is lovely).
If the word’s ending is unstressed is, es, as or ax the adjective or noun remains unchanged:
- o lápis (pencil) –> os llápis
- o tórax (chest) –> os tórax
- o atlas (atlas) –> os atlas
Example: Os alunos escrevem com canetas ou lápis (the pupils write with pens or pencils).