Kilometráž je v tomto terénu náročná.

In this sentence, kilometráž refers to the distance in kilometers or the overall mileage/route length being covered.

Depending on context, it can mean things like:

• the mileage of a route
• the number of kilometers involved
• how demanding the distance feels in a certain environment

So here it is not really about a car’s odometer. It is more likely talking about travel, hiking, cycling, running, or movement through difficult ground.

Because it agrees with kilometráž, which is a feminine singular noun.

In Czech, adjectives must match the noun in:

• gender
• number
• case

Here:

• kilometráž = feminine singular
• therefore the adjective is náročná = feminine singular

Compare:

• náročný terén = demanding terrain (masculine)
• náročná kilometráž = demanding mileage/distance (feminine)
• náročné stoupání = demanding climb/ascent (neuter)

A very common clue is the ending. Nouns ending in -áž are usually feminine, and kilometráž follows that pattern.

You can also confirm it from the sentence itself:

• kilometráž je náročná

The adjective náročná shows feminine agreement, so that tells you the noun is feminine as well.

Because the preposition v here means in, and when v expresses location, it takes the locative case.

So:

• terén = basic dictionary form
• v terénu = in the terrain / in this kind of terrain

And:

• tento changes to tomto in the locative masculine/neuter singular

So:

• v tomto terénu = in this terrain

It is the locative singular.

Why?

Because the preposition v often takes:

• locative when it means in / inside / within a place or setting
• accusative when there is movement into somewhere in some other expressions, but with v the everyday pattern is location = locative

Here there is no motion. The sentence describes a condition within this terrain, so Czech uses the locative:

• v tomto terénu

Yes. That word order is completely natural.

Czech word order is more flexible than English, and changing the order often changes emphasis, not the core meaning.

Compare:

• Kilometráž je v tomto terénu náročná.
  Focus starts with kilometráž.

• V tomto terénu je kilometráž náročná.
  Focus starts with the setting: in this terrain.

Both are correct. The version with V tomto terénu first may sound slightly more natural if you are contrasting terrains.

In the present tense, Czech normally keeps the verb být (to be) in this kind of sentence.

So:

• Kilometráž je náročná. = The mileage is demanding.

You cannot normally omit je here in standard Czech.

That is different from some other Slavic languages, where the present-tense to be may be dropped more often.

It can overlap with all three, but demanding or challenging is often the best match.

náročný / náročná / náročné suggests something that:

• requires effort
• is taxing
• is not easy physically or mentally

So in this sentence, it probably means the distance is hard to cover because of the terrain, not just that the number of kilometers is large.

It is slightly different from:

• těžký = hard, heavy, difficult
• obtížný = difficult
• náročný = demanding, requiring effort

It usually means terrain, ground conditions, or the nature of the landscape/surface.

Depending on context, terén can suggest:

• rough ground
• uneven landscape
• off-road conditions
• the physical environment you move through

So v tomto terénu does not just mean a place on a map. It implies that the character of the ground makes the route more demanding.

Yes. Some possible alternatives are:

• obtížná = difficult
• těžká = hard
• vyčerpávající = exhausting

But náročná is a very natural choice because it suggests that the distance becomes demanding because of the conditions, not necessarily because it is impossible.

So náročná sounds balanced and idiomatic here.

The structure is:

• Kilometráž = subject
• je = verb (is)
• v tomto terénu = adverbial phrase of setting/location
• náročná = predicate adjective

So literally the grammar is:

• Mileage/distance is in this terrain demanding

Natural English would reorder that, but the Czech structure is completely normal.

Yes. This pattern is very common:

[noun] + je + [adverbial phrase] + [adjective]

For example:

• Práce je dnes obtížná. = The work is difficult today.
• Jízda je v horách nebezpečná. = Driving is dangerous in the mountains.
• Trasa je po dešti náročná. = The route is demanding after rain.

So the sentence is a very useful model for describing conditions.