По: One Preposition, Many Meanings

По is one of those little words you meet on your first day and keep meeting for years. It turns up in front of streets, phones, weekdays, school subjects — and it seems to mean something different every time: along, on, by, according to. That can feel like a lot to carry around.

Here's what makes it manageable.

Underneath all those translations there's one physical idea. Picture your hand moving across a surface — not landing on a single spot, but sweeping over it. That sweep is по. A street, a phone line, a week of Mondays, a field of study: Russian treats each of them as a kind of surface, and по moves across it.

Keep that picture in mind and the long list of meanings turns into one thing seen from different angles.

One spot, or a sweep across?

The quickest way to feel по is to hold it up against в and на. Those two point to a single spot — where something is, or where it's going. По is the opposite kind of idea: not a spot at all, but the sweep across it.

• Кни́га на столе́. — The book is on the table. (a single spot)
• Кот хо́дит по столу́. — The cat walks around on the table. (across the surface)
• Я иду́ в парк. — I'm going to the park. (a destination)
• Я гуля́ю по па́рку. — I'm walking around the park. (across the space)

Same table, same park — but на and в put you at a point, while по sets you moving across it. (If в and на themselves still trip you up, they get their own full guide here: В vs На.)

First, the dative

One quick grammar note before the meanings. After по, the noun goes into the dative case, so its ending changes:

• парк (park) → по па́рку
• у́лица (street) → по у́лице
• мо́ре (sea) → по мо́рю

You'll meet these same endings again and again through the article. If you'd like the full set laid out, they're all here: The Dative Case.

Moving across a surface

This is the picture in its most literal form — по moving over a surface or through a space. English splits it across several words (along, around, down, through, over, on), and the one that fits depends on the scene:

• идти́ по у́лице — to walk down the street
• гуля́ть по го́роду — to wander around the city
• Ле́том мы путеше́ствовали по Ита́лии. — In summer we travelled around Italy.
• Де́ти бе́гали по всему́ до́му. — The kids were running all over the house.

Notice what stays the same: you're never heading to one point, you're moving across a space.

Travelling down a channel

From a surface it's a small step to a channel. When a voice or a signal travels through some medium, the sweep runs along that line — and Russian reaches for по:

• по телефо́ну — by phone / on the phone
• по ра́дио — on the radio
• по телеви́зору — on TV
• по интерне́ту — over the internet
• Отпра́вь мне докуме́нты по электро́нной по́чте. — Send me the documents by email.

Spread across the week

Now the "surface" is your calendar. For something that happens regularly, по spreads the action across a set of repeating days or times. The noun goes into the dative plural here:

• по понеде́льникам — on Mondays
• по выходны́м — at weekends
• по утра́м — in the mornings
• по пра́здникам — on holidays
• По вечера́м она́ мно́го чита́ет. — In the evenings she reads a lot.

(For one single day of the week, you'd use в + accusative — в понеде́льник, "on Monday." But for the repeating habit, it's по понеде́льникам.)

Across a whole subject

Here the surface is a field of knowledge, and по ranges over the whole of it — a book on, an exam in, a specialist in:

• уче́бник по хи́мии — a textbook on chemistry
• экза́мен по матема́тике — a maths exam
• ле́кция по исто́рии — a history lecture
• специали́ст по ма́ркетингу — a marketing specialist
• дома́шнее зада́ние по ру́сскому — homework in Russian
• У меня́ за́втра экза́мен по фи́зике. — I have a physics exam tomorrow.
• Она́ пи́шет кни́гу по психоло́гии. — She's writing a book on psychology.

One to each

Same sweep, only turned outward: по can spread one item across a group, giving or taking one per person:

• Возьми́те по одному́. — Take one each.
• Ка́ждому да́ли по конфе́те. — Everyone got a candy.
• Ма́ма дала́ де́тям по я́блоку. — Mum gave the children an apple each.

(Once bigger numbers come in — two each, five each — the grammar shifts around, but that belongs with the numbers topic. For now, just recognise the "one each" pattern.)

Along a rule, along a reason

Think of a plan, a schedule, even a habit as a line already laid down. По moves along that line — doing something the way the plan, the rule, or the routine sets out:

• по пла́ну — according to plan
• по зако́ну — by law
• по расписа́нию — on schedule
• по прогно́зу — according to the forecast
• Де́лай по пра́вилам. — Do it by the rules.
• Она́ де́лает всё по инстру́кции. — She does everything according to the instructions.

The same "following along" gives you по for a reason or cause — usually something unplanned:

• по оши́бке — by mistake
• по привы́чке — out of habit
• по боле́зни — due to illness
• Она́ пропусти́ла заня́тие по уважи́тельной причи́не. — She missed the class for a valid reason.
• Мы перенесли́ встре́чу по его́ про́сьбе. — We rescheduled the meeting at his request.
• Он купи́л э́то про́сто по глу́пости. — He bought that just out of foolishness.

Missing someone: скучать по

If you like, you can squint and keep the picture alive here too — the longing "travels across" toward the person you miss, spreading out to them. It's more romantic than grammatical, though. In plain terms, по is just the preposition скуча́ть happens to take. "To miss" someone or something is скуча́ть по + dative:

• скуча́ть по до́му — to miss home
• Я скуча́ю по тебе́. — I miss you.
• Мы скуча́ем по ле́ту. — We miss summer.
• Она́ скуча́ет по семье́. — She misses her family.
• Я о́чень скуча́ю по друзья́м. — I miss my friends a lot.

Just keep the по and put the dative after it — по тебе́, по вам, по нему́ — and you're set.

По- adverbs: the same sweep, frozen into one word

Now a family of words that look exactly like our preposition but behave differently: по-ру́сски, по-мо́ему, по-сво́ему. These are single words — adverbs, answering как? ("how?"), built with по- as a prefix on an adjective or a possessive.

The picture isn't gone here, though. It's frozen. Most of these grew out of real по + dative phrases: по-мо́ему is по моему́ [мне́нию] — "along my opinion"; по-но́вому runs along the new way; по-ру́сски follows the Russian one. The sweep still happens, only now it moves across a way of doing something instead of a street. What changed is the mechanics: two words became one, and no noun follows it any more.

Most of them end in -ому or -ему — the same ending a masculine adjective takes in the dative. One little group stands apart: the "in language X" adverbs, which end in -ски.

• по-ру́сски, по-англи́йски, по-испа́нски — in Russian, in English, in Spanish

Now the real question, the one a bare list never answers: why does Russian even need this по-…-ому form, when it already has tidy adverbs like бы́стро (quickly)? There are two different situations.

The first is when there's simply no plain adverb to fall back on. Ordinary adjectives make one just by adding -о: бы́стрый → бы́стро (quickly), ме́дленный → ме́дленно (slowly). But the possessives and the "which-one" words can't do that. There's no plain adverb from мой (my), свой (one's own), друго́й (other) or любо́й (any) — любо just isn't a word for "in any way." So for these, по-…-ому is the only way to build an "in [X] way" adverb:

• по-мо́ему, по-тво́ему, по-на́шему, по-ва́шему — in my opinion, in your opinion, in our opinion, in your (formal) opinion
• по-сво́ему — in one's own way
• по-друго́му — differently, in a different way
• по-любо́му — one way or another, anyway (colloquial)

The second situation is ordinary adjectives, where по-…-ому means "in the X way, X-style." A few things can happen here. Sometimes a plain adverb already exists and stays neutral, while the по- form is the colloquial one — бы́стрый gives you the everyday бы́стро (quickly), and по-бы́строму is the casual, "quick-and-rough" version. Sometimes the adjective has no everyday plain manner adverb, so the по- form is all there is (но́вый, ста́рый, ра́зный). And a few have simply hardened into set, idiomatic meanings. Here's the range:

• бы́стро → по-бы́строму — quickly → in a rush, quick and dirty (colloquial)
• про́сто → по-просто́му — simply → in a plain, no-frills way (colloquial)
• хорошо́ → по-хоро́шему — well → the nice way, amicably (idiomatic)
• пло́хо → по-плохо́му — badly → the hard way (idiomatic)
• по-но́вому, по-ста́рому — in a new way, in the old way
• по-ра́зному — in various ways
• по-пре́жнему — still, as before (idiomatic)
• по-настоя́щему — really, genuinely (idiomatic)

(A handful go one step further and fuse into a single written word — like потихо́ньку, "little by little.")

Here they are in a sentence or two:

• Он всё де́лает по-сво́ему. — He does everything his own way.
• Дава́й сде́лаем э́то по-бы́строму. — Let's do this quickly.
• По-любо́му, я приду́ на встре́чу. — One way or another, I'll be at the meeting.
• По-мо́ему, э́то отли́чная иде́я. — In my opinion, that's a great idea.

Two other cases, briefly

Nearly all of the above is по with the dative. Just twice you'll meet it with another case — recognise these and move on:

по + accusative — "up to / through (and including)." This is the по in the pairing с … по, "from … to," where the end point is included:

• Магази́н рабо́тает с понеде́льника по пя́тницу. — The shop is open from Monday to Friday.
• вода́ по коле́но — knee-deep water (water up to the knee)

по + prepositional — "upon / after" (formal and bookish). You'll see it mostly in official writing:

• по прибы́тии — upon arrival
• по оконча́нии — upon completion

Worth recognising when you read it; not worth drilling yet.

The dative по at a glance

The one picture behind all of it

So по isn't a pile of unrelated rules. It's one idea showing up in a lot of places: something moving across. A street, a phone line, the days of your week, a subject you're studying. Even the по- adverbs are that same sweep, just frozen inside a single word. The one place the picture really stops working is скуча́ть по, where по is simply the preposition the verb takes. Everywhere else, when you see по with a dative, look for that movement across. Once you can feel it, one of Russian's busiest little words stops being a puzzle.