Mobilní tarif je vlastně levný.

Here vlastně means something like actually, really, or when you think about it.

So Mobilní tarif je vlastně levný. is not just a flat statement that the plan is cheap. It suggests a small correction, realization, or reconsideration, such as:

• The mobile plan is actually cheap.
• The mobile plan is really quite cheap.
• Come to think of it, the mobile plan is cheap.

In everyday Czech, vlastně is very common and can be a bit flexible in tone.

Czech does not use articles like English the and a/an.

So mobilní tarif can mean:

• a mobile plan
• the mobile plan

The exact meaning depends on context. Czech speakers rely on context, word order, and shared knowledge instead of articles.

It is in the nominative case, because it is the subject of the sentence.

• mobilní tarif = the mobile plan
• je = is
• vlastně levný = actually cheap

So the structure is basically:

[subject in nominative] + [form of být] + [description]

Because levný is an adjective, and here it describes the noun tarif.

• levný = cheap (adjective)
• levně = cheaply (adverb)

In this sentence, we need an adjective because we are saying what the mobile plan is:

• Tarif je levný. = The plan is cheap.

If you used levně, that would be an adverb, which would not fit here.

The adjective has to agree with the noun it describes.

Tarif is:

• masculine
• singular
• inanimate

So the correct form is levný.

Compare:

• levný tarif = cheap plan
• levná služba = cheap service
• levné volání = cheap calling / cheap calls

So the ending changes depending on gender and number.

Mobilní is a different adjective pattern from levný.

In Czech, some adjectives are hard adjectives and some are soft adjectives.

• levný follows a hard-adjective pattern
• mobilní follows a soft-adjective pattern

That is why you get:

• mobilní tarif
• mobilního tarifu
• mobilním tarifem

The -ní ending is normal for this type of adjective.

In standard Czech, je is normally required here.

• Mobilní tarif je levný. = correct
• Mobilní tarif levný. = not standard as a normal complete sentence

Unlike some languages, Czech usually does not drop the present tense of to be in this kind of sentence.

The given word order is the most neutral and natural one:

Mobilní tarif je vlastně levný.

Czech word order is flexible, but changing it usually changes the emphasis.

For example:

• Mobilní tarif je vlastně levný. = neutral
• Vlastně je mobilní tarif levný. = stronger emphasis on actually
• Mobilní tarif je levný. = same statement, but without the nuance of vlastně

So yes, the word order can change, but the original version is a very normal default sentence.

Not always in the narrow English sense. In Czech, tarif often means a plan, pricing plan, or rate.

So in the context of phones:

• mobilní tarif = mobile plan / cell phone plan

A literal English word like tariff would usually sound less natural in everyday English, even though the Czech word is related.

A rough pronunciation is VLAS-tnye.

A few helpful points:

• Stress in Czech is almost always on the first syllable: VLAS-tně
• ě after n makes the sound ně, roughly like nye
• The stn cluster can feel difficult for English speakers, so it may take practice

So vlastně is approximately:

VLAS-tnye

That is only an approximation, but it is a useful starting point.

A rough English-friendly pronunciation would be:

MO-bil-nee TA-rif ye VLAS-tnye LEV-nee

A few details:

• mobilní = MO-bil-nee
• tarif = TA-rif
• je = ye
• vlastně = VLAS-tnye
• levný = LEV-nee

Czech stress is normally on the first syllable of each word, though in connected speech the rhythm is smoother than this breakdown suggests.

You usually should use levný here.

• levný = neutral, standard word for cheap / inexpensive
• laciný = can sound more negative, like cheap in the sense of low-quality, tacky, or cheesy

So:

• Mobilní tarif je levný. = normal and natural
• Mobilní tarif je laciný. = possible, but it may sound odd or negative depending on context

For a mobile plan, levný is the better choice.