Reciprocal 'Each Other' (Один Одного)

When two parties act on each other — "they love each other," "we help one another" — English uses a fixed little phrase: each other or one another, unchanging no matter the grammar around it. Ukrainian builds the same idea out of two words that both do work: a first word, оди́н (literally "one"), matched to the gender of the group, and a second word, о́дного, that declines for whatever case the verb or preposition needs. The result is a frame that inflects inside itself: оди́н о́дного "each other" (acc), оди́н о́дному "to each other" (dat), оди́н з о́дним "with each other" (instr). This page shows the gender-matched first half, the case-driven second half, and the rule that surprises every learner — the preposition goes between the two parts.

The frame: a fixed оди́н + a declining о́дного

Think of "each other" in Ukrainian as a relationship between two members of a group, spelled out one at a time: "one … the other." The first оди́н stands for "one of them" and takes the gender of the people involved; the second о́дного stands for "the other" and takes the case the sentence assigns. So the two halves carry different jobs: the first marks who, the second marks what role.

For the basic "each other" as a direct object (accusative), the three gender shapes are:

The second part declines for case

The whole grammatical action happens in the second word. Whatever case the verb or preposition would assign to a normal object, the о́дного part takes it — exactly as the pronoun оди́н "one" declines on its own. The first part usually stays put as оди́н / одна́ / одне́, naming the gender; it is the second part that moves through the cases.

Here is the masculine/mixed frame across the cases (the second part is the form of оди́н "one" in that case):

Notice that genitive and accusative share о́дного (animacy makes them identical for people), while the dative is о́дному and the instrumental о́дним — the very endings the numeral/pronoun оди́н takes when it declines alone.

The preposition goes between the two parts

This is the rule that has no English parallel and that learners almost always get wrong. When the reciprocal needs a preposition, the preposition does not sit in front of the whole phrase. It slips into the middle, between оди́н and о́дного. The first part stays a bare nominative-looking оди́н; the preposition plus the case it governs land on the second part.

So the mental model is: оди́н [PREPOSITION CASE-FORM]. You set the gender with the first word, then build a normal prepositional phrase out of the second word. If you ever catch yourself writing про оди́н о́дного or з оди́н о́дним, you have put the preposition in the wrong slot.

Reciprocal оди́н о́дного vs reflexive себе́ / -ся

English speakers blur these because English itself splits the work oddly: themselves is reflexive, each other is reciprocal, and learners often reach for the wrong one. Ukrainian keeps them strictly apart.

• себе́ / -ся = reflexive: each person acts on himself/herself. Вони́ ми́ються = "they wash (themselves)" — each washes their own body.
• оди́н о́дного = reciprocal: the people act on each other, crosswise. Вони́ ми́ють оди́н о́дного = "they wash each other."

There is also an overlap to be aware of: some -ся verbs are inherently reciprocal and already mean "each other," so adding оди́н о́дного would be redundant. Зустріча́тися "to meet (one another)," цілува́тися "to kiss," обійма́тися "to hug," листува́тися "to correspond," мири́тися "to make up," свари́тися "to quarrel" — these build the reciprocity into the verb.

Use the explicit оди́н о́дного when you want to spotlight the mutuality, when the verb is not one of the inherently reciprocal -ся verbs, or when a case/preposition is needed that the bare verb can't express (про о́дного, оди́н від о́дного).

Source-language comparison

For an English speaker, three habits have to change. (1) Each other is two words that inflect, not a frozen phrase: the first agrees in gender (оди́н / одна́ / одне́), the second in case (о́дного / о́дному / о́дним). (2) The preposition goes in the middle — оди́н про о́дного, never про оди́н о́дного — which feels backwards to an English ear that says "about each other" as a block. (3) Don't confuse it with reflexive *themselves: Ukrainian uses себе́ / -ся for "on oneself" and оди́н о́дного for "on each other," and they are not interchangeable.

For a Russian speaker, the construction maps closely onto друг дру́га, where the first part is likewise fixed and the second declines (друг дру́гу, друг с дру́гом). The Ukrainian frame is built on оди́н, not друг, and the careful gender agreement (одна́ о́дну, одне́ о́дного) is more actively observed in standard Ukrainian — so produce the Ukrainian оди́н о́дного / одна́ о́дну / одне́ о́дного rather than a calqued друг дру́га, and keep the apostrophe-free о́дним, о́дному in their Ukrainian shape.

Common Mistakes

Key Takeaways

• "Each other" is a two-word frame: a gender-matched first part (оди́н / одна́ / одне́) plus a case-declining second part (о́дного / о́дну / о́дному / о́дним).
• The first part marks gender, the second part marks case — оди́н о́дному (dat), оди́н з о́дним (instr), оди́н на о́дному (loc).
• For a mixed-sex pair the careful form is одне́ о́дного; males-only оди́н о́дного, females-only одна́ о́дну.
• The preposition goes between the two parts: оди́н про о́дного, оди́н до о́дного, оди́н за о́дним — never in front of the whole phrase.
• Keep reciprocal оди́н о́дного ("on each other") apart from reflexive себе́ / -ся ("on oneself"); and remember that зустріча́тися, цілува́тися, свари́тися are already reciprocal on their own.