Tato místnost je vhodná pro tuto činnost.

Because they are the same demonstrative pronoun ten / ta / to in different cases.

• tato místnost = this room
  
  • místnost is the subject, so it is in the nominative
• pro tuto činnost = for this activity
  • after pro, Czech uses the accusative

So:

• tato = feminine singular nominative
• tuto = feminine singular accusative

Both místnost and činnost are feminine singular nouns, but they play different roles in the sentence, so the forms differ.

Because adjectives in Czech must agree with the noun they describe in gender, number, and case.

Here, vhodná describes místnost:

• místnost = feminine singular
• it is in the nominative
• so the adjective must also be feminine singular nominative

That is why you get:

• masculine: vhodný
• feminine: vhodná
• neuter: vhodné

So vhodná matches místnost.

• místnost is in the nominative, because it is the subject of the sentence.
• činnost is in the accusative, because it comes after the preposition pro.

So the structure is:

• Tato místnost = nominative subject
• je vhodná = verb + predicate adjective
• pro tuto činnost = prepositional phrase with pro + accusative

Yes, pro takes the accusative.

That is why you have:

• pro tuto činnost not
• pro tato činnost
• pro této činnosti

Some more examples:

• pro mě = for me
• pro děti = for children
• pro tu firmu = for that company

So this sentence is a very good example of pro + accusative.

Because the subject is singular:

• Tato místnost = this room = one room

So the verb být must also be singular:

• je = is

If the subject were plural, you would use jsou:

• Tyto místnosti jsou vhodné pro tuto činnost.
• These rooms are suitable for this activity.

Here are the dictionary forms:

• tato / tuto → dictionary form: ten (this/that, depending on context)
• místnost → místnost (room)
• je → být (to be)
• vhodná → vhodný (suitable, appropriate)
• pro → pro (for)
• činnost → činnost (activity, operation, task)

This is useful because in Czech you often see changed forms in real sentences, but dictionaries usually list the base form.

Yes. In Czech, many feminine nouns do end in -a, but not all of them.

Both místnost and činnost are feminine nouns ending in a consonant-like written form. This is normal in Czech. In fact, many nouns ending in -ost are feminine, for example:

• radost = joy
• rychlost = speed
• možnost = possibility
• činnost = activity

So you simply need to learn their gender as part of the noun.

Yes, Czech word order is fairly flexible, though not completely free. The original sentence is a very natural neutral order:

• Tato místnost je vhodná pro tuto činnost.

But you could also say:

• Tato místnost je pro tuto činnost vhodná.

This version puts a bit more emphasis on for this activity before vhodná.

Both are correct. The original version is probably the most straightforward for a learner.

Yes. That would be more colloquial.

Compare:

• tato / tuto = more formal, written, careful style
• tahle / tuhle = more everyday spoken Czech

So:

• Tato místnost je vhodná pro tuto činnost.
  sounds neutral to formal
• Tahle místnost je vhodná pro tuhle činnost.
  sounds more conversational

A learner should understand both.

Not exactly.

• vhodný means suitable, appropriate, fitting
• dobrý means good

In this sentence, vhodná is better because the idea is not just that the room is good, but that it is appropriate for a specific purpose.

Compare:

• To je dobrá místnost. = That is a good room.
• Ta místnost je vhodná pro tuto činnost. = That room is suitable for this activity.

So vhodný is more precise here.

Yes, in many contexts you can say:

• Tato místnost je vhodná k této činnosti.

This is also correct. However, there is a slight difference in feel:

• pro + accusative often means for in the sense of suitability, purpose, intended use
• k + dative can also mean for / for use in relation to, and is common with words like vhodný

So both are possible, but pro tuto činnost is very straightforward and easy to understand.

The grammar changes, though:

• pro tuto činnost = accusative
• k této činnosti = dative

In Czech, the main word stress is usually on the first syllable of each word.

So roughly:

• TA-to
• MÍST-nost
• je
• VHOD-ná
• pro
• TU-to
• ČIN-nost

A useful thing for English speakers to remember is that Czech stress is much more regular than English stress. Even if vowel length matters, the stress itself usually stays on the first syllable.

Vhodná is an adjective, not part of the verb itself.

The structure is:

• je = the verb to be
• vhodná = an adjective describing the subject

Together they form a predicate meaning:

• is suitable

This is similar to English:

• The room is suitable.

So grammatically:

• místnost = subject
• je = verb
• vhodná = predicate adjective

Because Czech has no articles.

English says things like:

• the room
• a room
• this room

Czech does not have separate words for the and a. Instead, meaning is shown through context or with words like tento / tato / toto when you want to specify this.

So:

• místnost can mean a room or the room, depending on context
• tato místnost clearly means this room

That is one of the biggest differences English speakers notice when learning Czech.