Numerals as Determiners

When a number sits in front of a noun — two coffees, the first day, half a kilo — it is doing a determiner's job: telling you how many or which one. This page is about numbers in exactly that role. For the full inventory of how to count (forms, spelling, big numbers), see the Numbers pages; here the focus is the one thing that trips up English speakers, who are used to numbers that never change shape: a handful of Portuguese numerals agree in gender, and you must get that agreement right every single time.

Most cardinals are invariable — but not all

The good news first: the vast majority of cardinal numbers in Portuguese never change. Três, quatro, cinco, dez, vinte, mil — all fixed, whatever the noun. The exceptions are short and worth memorizing as a set:

So the gendered cardinals are 1, 2, and the hundreds from 200 to 900. Everything between — 3 through 199 except for the um/uma and dois/duas embedded in them — is invariable.

Dois vs duas — the most common trap

Because English "two" never changes, learners overwhelmingly default to dois for everything. But dois is masculine only; with a feminine noun you must say duas:

This even reaches inside compounds: vinte e *duas páginas (22 pages), duzentas e **duas pessoas. The embedded *dois/duas still agrees.

Um/uma — article and numeral in one

The form um/uma does double duty: it is the indefinite article ("a/an") and the number "one." Context tells them apart, and often the line is blurry — um café can mean "a coffee" or "one coffee." When you want to stress the count, BR adds só / apenas ("only one") or uses stress in speech:

Whether it leans "article" or "number," it always agrees: um with masculine, uma with feminine.

Ordinals — they agree, and they go in front

Ordinals (primeiro, segundo, terceiro …) all agree in gender and number, and as determiners they normally sit before the noun, taking the definite article:

That last example shows ordinals stacking with cardinals — and both agreeing. For the full list of ordinal forms and the spoken habit of replacing high ordinals with cardinals (apartamento vinte e um for "21st apartment"), see the Ordinal Numbers page.

Meio / meia — "half" agrees too

Meio ("half") is an adjective-numeral that agrees with what it measures. With a feminine noun it becomes meia:

There is also a famous BR quirk: on the phone or when dictating numbers, Brazilians say meia for the digit 6, short for meia dúzia ("half a dozen"), to avoid confusing seis with três:

Collectives — counting with a noun of quantity

Some "numbers" are really nouns of quantity, joined to what they count with de: uma dúzia de ovos, um par de sapatos, uma centena de pessoas. These take an article like any noun and the agreement is on the collective noun, not the counted thing:

(For the broader family — dezena, centena, milhar — see Collective Numerals.)

Comparison with English

English numerals are completely invariable: one, two, three, two hundred never change for gender, and ordinals (first, second) are fixed too. Portuguese asks for agreement in three pockets — um/uma, dois/duas, the hundreds — plus meio/meia and all the ordinals. Everything else is invariable, so the rule is genuinely small; the difficulty is purely that it is unfamiliar, since English never trains you to think of "two" as having a gender. The single highest-frequency error you will make and hear corrected is dois where a feminine noun demands duas.

Common Mistakes

Key Takeaways

• Most cardinals are invariable; only um/uma, dois/duas, and the hundreds (duzentos/duzentas …) agree in gender.
• Embedded dois/duas still agrees inside larger numbers: vinte e duas páginas.
• um/uma is both the indefinite article and the number "one"; add só/apenas to force the counting sense.
• Ordinals agree and sit before the noun with the article: o primeiro dia, a terceira tentativa.
• meio/meia ("half") agrees: meia hora, meio quilo; spoken BR also uses meia for the digit 6.
• Collectives (uma dúzia de, um par de) join the counted noun with de.