Learn Hardcore Russian: Мы идём по тротуару между домом и парком. - We are walking on the sidewalk between the house and the park.

The correct form is идём (with ё), but in everyday Russian ё is often written as е. So you will usually see идем in print, but it is still pronounced идём.

Key points:

The verb is идти (to go on foot in one direction).
Мы идём = we are going / we are walking.
Conjugation (with correct pronunciation):
- я иду́
- ты идёшь
- он/она идёт
- мы идём
- вы идёте
- они иду́т

So orthographically, both идем (informal spelling) and идём (full spelling) are used in texts, but you must pronounce it with ё: [ид‑ЙОМ].

What is the difference between мы идём and мы ходим? Both seem to mean “we are going / walking”.

Both involve going on foot, but they are not interchangeable:

Мы идём – one specific movement in one direction, right now or in a specific situation.
- We are walking (now) / we are on our way (to some place).
Мы ходим – repeated, habitual, or multi‑directional movement.
- We (regularly) go / we usually walk (there and back, from time to time).

Examples:

Мы идём в парк. – We’re going to the park (now, this time).
Мы ходим в парк по выходным. – We go to the park on weekends (as a habit).

In your sentence, мы идём по тротуару… clearly describes a current, single walk along the sidewalk, so идём is correct.

Why do we use по тротуару and not something like на тротуаре or вдоль тротуара?

All three are possible in Russian, but they mean slightly different things:

по тротуару – along the sidewalk / on the sidewalk as a route
Focus: the sidewalk is the path you are moving along.
на тротуаре – on the sidewalk
Focus: location, not movement along it.
вдоль тротуара – along (alongside) the sidewalk
Focus: you are walking beside it, not necessarily on it.

So:

Мы идём по тротуару. – We are walking on/along the sidewalk (using it as our route).
Мы стоим на тротуаре. – We are on the sidewalk (standing).
Мы идём вдоль тротуара. – We are walking along the sidewalk (maybe on the road right next to it).

For movement on a surface as a route, по is the most natural choice.

What case is тротуару, and why is that case used after по here?

Тротуару is in the dative case (singular).

With the preposition по, Russian usually uses the dative case to express movement along or over a surface, or within some area:

идти по тротуару – to walk along the sidewalk
бежать по дороге – to run along the road
гулять по парку – to stroll in/around the park

So here:

Nominative (dictionary form): тротуар (sidewalk)
Dative singular: тротуару

Pattern: по + dative → movement along/over something or within some area.

Can по ever use a different case, or is it always dative?

По is a very flexible preposition and can take different cases depending on meaning:

Dative (most common):
- Movement along/over: по тротуару, по дороге
- Distribution: разделить по группам – divide into groups
- Communication: по телефону, по телевизору
Prepositional (mostly in older or set expressions):
- по приезде, по окончании – after arrival, after completion
Accusative appears in some fixed expressions and older style, but for a learner the main thing to remember is:
For movement along a surface or route, use по + dative.

Why are домом and парком in that form? Why not just между дом и парк?

Домом and парком are in the instrumental case.

The preposition между (between) in standard modern Russian normally requires the instrumental case:

между домом и парком – between the house and the park
между столом и окном – between the table and the window
между мной и тобой – between me and you

So:

Nominative: дом, парк
Instrumental: домом, парком

Saying между дом и парк is ungrammatical. In informal speech you may sometimes hear между дома и парка (genitive), but for correct standard Russian you should use между + instrumental.

What does между домом и парком express exactly? Is it physical space or something more abstract?

In this sentence it clearly expresses physical location: you are walking on the sidewalk that lies in the space between a house and a park.

However, между can also be used abstractly:

между друзьями – between friends
между нами – between us
между двумя событиями – between two events (time or conceptual distance)

In your example it is the straightforward, spatial meaning: in the area between the house and the park.

Could the subject мы be omitted? Would Идём по тротуару между домом и парком still be correct?

Yes, you can omit мы in many contexts:

Мы идём по тротуару…
Идём по тротуару…

Both are grammatically correct. Russian is a pro‑drop language: the verb ending ‑ём already shows the subject is мы (we). You include мы if you want to be explicit or emphatic, or when context is unclear.

In a dialogue, for example:

Куда пойдём? – Where shall we go?
Идём по тротуару между домом и парком. – Let’s walk along the sidewalk between the house and the park.

Here dropping мы sounds natural.

Is there any difference in meaning or emphasis if I change the word order, like Мы идём между домом и парком по тротуару?

All of these are grammatically possible, but they differ in emphasis and naturalness:

Most neutral:
- Мы идём по тротуару между домом и парком.
Also acceptable (slightly different emphasis):
- Мы идём между домом и парком по тротуару.

In the second version, между домом и парком is heard earlier, so the listener first imagines the space “between the house and the park,” and then learns that this space is specifically a sidewalk. In the original, the listener first gets the route (по тротуару) and then its location (между домом и парком).

All prepositional phrases like this are relatively flexible in Russian, but the original order is the most typical and smooth.

How do I pronounce the whole sentence correctly, especially the stress?

Pronunciation with stress marks:

Мы идём по тротуáру междý домóм и пáрком.

мы – [мы]
идём – [ид’ём] (stress on ём)
по – [по]
тротуáру – [тратуáру] or [тратуáру] (stress on á)
междý – [междý] (stress on у́)
домóм – [дамóм] (stress on о́)
и – [и]
пáрком – [пáркам] (stress on а́)

Russian stress is unpredictable, so it is useful to memorize word stress along with vocabulary: идём, тротуáр, междý, домóм, пáрком.

Are дом, парк, and тротуар all the same gender? How do their cases look in general?

Yes, all three are masculine inanimate nouns ending in a consonant.

Their singular case forms (most common ones):

дом (house)

Nominative: дом
Genitive: дома
Dative: дому
Accusative: дом
Instrumental: домом
Prepositional: о доме

парк (park)

Nominative: парк
Genitive: парка
Dative: парку
Accusative: парк
Instrumental: парком
Prepositional: о парке

тротуар (sidewalk)

Nominative: тротуар
Genitive: тротуара
Dative: тротуару
Accusative: тротуар
Instrumental: тротуаром
Prepositional: о тротуаре

Your sentence uses:

тротуару – dative (after по)
домом, парком – instrumental (after между).