Copii or copiii?

In neutral contemporary Standard Romanian, copil means child, copii is the unarticulated plural, and copiii is the definite plural. Compare Doi copii se joacă în parc. (Two children are playing in the park.) with Copiii se joacă în parc. (The children are playing in the park.)

What do copii and copiii mean?

Use copii for the basic plural when the group is not marked as definite, and use copiii when the noun means an identified group: the children.

Romanian can express an indefinite plural with niște copii (some children), with a numeral such as doi copii (two children), or with a bare plural in a suitable context: În curte sunt copii. (There are children in the yard.) The noun spelling in all these unarticulated phrases is copii, not copiii.

How is copiii formed?

Treat copii as the plural form to learn, then add the attached definite article -i to get copiii.

1. Start with the singular noun: un copil (a child). Its plural is not formed as copili; the standard plural is copii.
2. Use copii after a numeral or niște: trei copii (three children), niște copii (some children).
3. Add the definite article -i when the group is identified: copii + -i gives copiii, as in Copiii au ajuns. (The children have arrived.)

This is why the final letters are easy to count but not interchangeable: copii has two final is, while copiii has three. The third i is not an optional extra; it is the definite article. For the wider article system, see the Romanian definite article.

How do you choose the form in a sentence?

First identify whether the noun phrase is unarticulated or definite, then check the words that determine it: numerals and niște point to copii, while a known group, a postposed possessive, or the bare definite noun points to copiii.

• If a numeral comes directly before the noun, use copii: doi copii, cei trei copii. Do not write doi copiii. In cei trei copii, cei carries the definite meaning, so the noun still stays copii.
• If niște comes before the noun, use copii: niște copii au intrat în clasă (some children entered the classroom).
• If the listener can identify the group and the noun itself carries the definite article, use copiii: Copiii au intrat în clasă. (The children entered the classroom.)
• A possessive after the noun normally appears with the definite form: copiii mei (my children), copiii voștri (your children).

What does the spelling tell you about pronunciation?

The extra letter in copiii reflects a real morphological difference, and it also affects the recommended pronunciation. In copii, the final -ii forms one syllable as a descending diphthong; in copiii, DOOM3 recommends pronouncing the ending with two syllabic i vowels. This pronunciation clue can help, but spelling and sentence meaning remain the reliable diagnostics.

Do not assume that every pair of final is has the same pronunciation. Romanian uses several i letters for different grammatical jobs, and speech may reduce contrasts in fast or casual delivery. Write the form required by the noun phrase, not the form that seems easiest to hear.

What are the important cautions?

• A modifier does not automatically force the definite plural. Compare Copii dintr-o clasă vecină așteaptă autobuzul. (Children from a neighboring class are waiting for the bus.) with Copiii din clasa vecină așteaptă autobuzul. (The children from the neighboring class are waiting for the bus.). The article and the intended reference matter.
• The English word the is not always shown by a final -i on this noun. Cei doi copii means the two children, but cei is the definite determiner and the noun remains copii.
• The plural spelling copii can also mean copies, the plural of copie. Context and stress distinguish the two words in speech: Am imprimat două copii ale documentului. (I printed two copies of the document.)
• Do not confuse the definite plural copiii with the plural genitive-dative copiilor: Le-am dat copiilor cărți. (I gave the children books.) For a fuller plural overview, see How Romanian noun plurals work.

A quick decision rule

If you can naturally put doi, trei, or niște before the noun, write copii. If you mean an identified group and no other determiner carries definiteness, write copiii. If another determiner already carries definiteness, as in cei doi copii, keep the noun as copii.