Tento mobilní tarif je neomezený.

Tento means this.

It is the masculine singular nominative form of the demonstrative pronoun ten / tento. In this sentence it matches tarif, which is a masculine inanimate singular noun.

So:

• tento tarif = this plan / this tariff

Czech uses different forms of this depending on the gender, number, and case of the noun:

• tento tarif = this plan
• tato služba = this service
• toto číslo = this number

You may also hear tenhle or tenhleten in informal speech, but tento is a standard, neutral written/spoken form.

Mobilní is the normal adjective meaning mobile or cellular/mobile-phone-related.

So mobilní tarif means something like:

• mobile plan
• mobile tariff
• cellphone plan

In Czech, mobilní is a very common adjective used in combinations like:

• mobilní telefon = mobile phone
• mobilní síť = mobile network
• mobilní tarif = mobile plan

A form like mobilový is not the normal word here.

Not exactly.

In Czech, tarif often means:

• a pricing plan
• a rate
• a service plan

In the context of phone services, mobilní tarif is the usual term for a mobile plan.

So while English tariff exists, the natural translation in this context is usually plan rather than tariff.

Je is the 3rd person singular form of být = to be.

So:

• je = is

In the present tense, Czech normally does use the verb to be in sentences like this:

• Tarif je neomezený. = The plan is unlimited.

Unlike Russian, for example, Czech does not usually omit is in standard present-tense sentences.

Neomezený literally means not limited or unlimited.

It is built from:

• omezit = to limit / restrict
• omezený = limited / restricted
• ne- = not / un-

So:

• omezený = limited
• neomezený = unlimited

This is a very common pattern in Czech: adding ne- to create the opposite meaning.

Because it agrees with tarif.

In Czech, adjectives must match the noun they describe in:

• gender
• number
• case

Here, tarif is:

• masculine
• singular
• nominative

So the adjective takes the masculine singular nominative ending -ý:

• neomezený tarif
• tarif je neomezený

If the noun changed, the adjective would change too:

• ta služba je neomezená = that service is unlimited
• to volání je neomezené = that calling is unlimited

Here neomezený is not directly modifying the noun inside the noun phrase. It is part of the predicate after to be.

Compare:

• neomezený tarif = an unlimited plan
  
  • here the adjective is directly before the noun
• tarif je neomezený = the plan is unlimited
  
  • here the adjective comes after je

This works similarly to English:

• an unlimited plan
• the plan is unlimited

So the position changes depending on the structure of the sentence.

Yes, absolutely.

Tento tarif je neomezený is grammatically correct and natural if the context already makes it clear that you are talking about a mobile plan.

Adding mobilní just makes it more specific:

• Tento tarif je neomezený. = This plan is unlimited.
• Tento mobilní tarif je neomezený. = This mobile plan is unlimited.

Czech does not have articles.

So there is no separate word for a or the.

Instead, Czech often shows definiteness through:

• context
• word order
• demonstratives like ten, tento

In this sentence, tento already tells you it means this mobile plan, so no article is needed.

It is in the nominative case.

Why? Because tarif is the subject of the sentence:

• Tento mobilní tarif = the thing being talked about
• je neomezený = is unlimited

The subject of a Czech sentence is normally in the nominative.

Also, the predicate adjective neomezený matches it in nominative form.

Yes, mobilní is also agreeing with tarif, but its form happens to stay mobilní.

Some Czech adjectives have endings like:

• -ý / -á / -é

But adjectives like mobilní belong to a different pattern, where the masculine singular nominative form is -í:

• mobilní tarif
• mobilní služba
• mobilní připojení

So it is agreeing, but the form does not change in the same obvious way as neomezený / neomezená / neomezené.

Yes, Czech word order is flexible, but the emphasis changes.

Neutral, standard order:

• Tento mobilní tarif je neomezený.

Also possible:

• Mobilní tarif je neomezený.
  If this is not important or is understood from context.

More marked/emphatic:

• Neomezený je tento mobilní tarif.
  This strongly emphasizes unlimited.

Czech often uses word order to show focus and emphasis, much more than English does.

A simple pronunciation guide:

• Tento ≈ TEN-to
• mobilní ≈ MO-bil-nee
• tarif ≈ TA-rif
• je ≈ ye
• neomezený ≈ ne-o-me-ze-nee

A rough full pronunciation:

TEN-to MO-bil-nee TA-rif ye ne-o-me-ze-nee

A few useful notes:

• Czech stress usually falls on the first syllable of each word.
• j is pronounced like English y in yes.
• í and ý are both long vowels.

Both can often be translated as this or that, depending on context, which can be confusing for English speakers.

Very roughly:

• ten = that / the / sometimes this in everyday speech
• tento = this, more explicitly

In many situations, tento sounds a bit more precise or formal than ten.

So:

• ten tarif = that plan / the plan / sometimes this plan
• tento tarif = this plan

In careful textbook-style Czech, tento is the clearest match for English this.