'Both': oba and obě

The Czech word for "both" is oba (masculine) / obě (feminine and neuter). Unlike English both, which never changes, the Czech word inflects — it has a gender split in the nominative and a special set of oblique forms (obou, oběma) that preserve fossilized dual endings from an older stage of the language. In almost every respect it behaves exactly like dva / dvě ("two"), so if you know how dva works, you already know most of oba. This page lays out the gender choice, the full declension, the verb agreement, and the dual relics that survive in fixed phrases.

For the parallel patterns with the actual number two, see The numbers two to four.

The gender split: oba vs. obě

In the nominative (and the identical accusative for inanimates), the form depends on the gender of the noun, exactly mirroring dva / dvě:

• oba — with masculine nouns (animate and inanimate): oba bratři, oba domy
• obě — with feminine and neuter nouns: obě sestry, obě okna

So masculine takes oba, while feminine and neuter share obě. The noun itself stands in the nominative plural, not the genitive — this is a key difference from "five and up," which would force the genitive.

Notice that obě covers both sestry (feminine) and okna (neuter) — the same form for two genders, just as dvě does. Only masculine gets the distinct oba.

Verb agreement: plural, and animate -i for men

Because "both" inherently refers to two things, the verb is always plural. And in the past tense, the l-participle follows normal plural agreement: masculine animate takes -i, masculine inanimate and feminine take -y, neuter takes -a.

In Oba přišli, the -i ending marks masculine animate subjects (men/boys). In Obě se těšily, the -y marks feminine. And in Obě auta zastavila, the neuter plural l-participle is -a (zastavila) — the same distinct neuter-plural cell you meet throughout Czech, agreeing with neuter auta.

Standing alone: "both of them"

Oba and obě can stand on their own as a pronoun meaning "both (of them)," without a following noun. The gender of the form still reflects the gender of the people or things referred to:

When the group is mixed-gender (e.g., a man and a woman), Czech defaults to the masculine oba, as it does for mixed groups generally.

The declension: obou and oběma

This is where "both" reveals its archaic core. In the oblique cases, oba/obě collapses into just two forms — obou and oběma — which are the same for all genders. These are old dual endings, and they pattern precisely like the oblique forms of dva (dvou, dvěma).

So the genitive and locative share obou, while the dative and instrumental share oběma. Gender stops mattering once you leave the nominative/accusative — obou and oběma serve masculine, feminine, and neuter alike.

The noun that follows agrees in the same case. So after the genitive obou you get a genitive noun (obou stran), and after the dative oběma you get a dative noun (oběma dětem). This is ordinary case agreement; see Case propagation in numerals for the general principle.

The dual relics: oběma rukama, oběma očima

A few body parts that come in pairs — hands, eyes, ears, legs — keep genuine dual instrumental endings in -ma, and oba pairs with them beautifully because oběma is itself a dual form. These are not regular plurals; they are living fossils:

The forms rukama (hands), očima (eyes), ušima (ears), and nohama (legs/feet) are the instrumental dual, and oběma is exactly the form that goes with them. You will hear oběma rukama constantly; it is the normal way to say "with both hands."

Emphatic "oba dva"

To stress "both" — "both of them, the two of them together" — Czech often adds the number: oba dva (masc.), obě dvě (fem./neut.). It is colloquial and emphatic, roughly English "the both of them" or "both the two of them." Both parts inflect together in the oblique cases (obou dvou, oběma dvěma), though the bare oba/obě is more common in careful writing.

Common mistakes

The most common error for English speakers is leaving "both" uninflected — using oba for everything because English both never changes. With feminine or neuter nouns you must switch to obě: obě sestry, obě okna, never oba sestry.

Leaving "both" in the nominative inside an oblique phrase — z oba strany — is wrong twice over: the preposition z demands the genitive, so it must be obou, and the noun follows suit (stran).

Using obou where oběma is needed (or vice versa) is a frequent slip. Remember the two-form split: obou = genitive/locative, oběma = dative/instrumental. The preposition s ("with") takes the instrumental, so it must be oběma.

Replacing the dual rukama with a regular plural — oběma rukami — sounds wrong to native ears for hands; the paired body parts keep their dual -ma, and oběma matches them.

Adding a singular verb because "both" feels like one unit — treating it like English "each" — gives Oba má pravdu, which is wrong. "Both" is inherently two, so the verb is always plural.

Key takeaways

• "Both" is oba (masculine) / obě (feminine + neuter) — the gender split mirrors dva / dvě.
• The noun stands in the nominative plural, and the verb is always plural (Oba přišli, Obě přišly, neuter Obě auta zastavila).
• Oblique cases collapse to two gender-neutral forms: obou (genitive/locative) and oběma (dative/instrumental).
• The dual lives on in oběma rukama, oběma očima — paired body parts with instrumental dual -ma.
• oba dva / obě dvě is the emphatic, colloquial "both of them."