Filtr je čistý.

Because in Filtr je čistý, čistý is a predicate adjective: it describes the subject after the verb je = is.

• Filtr je čistý = The filter is clean
• čistý filtr = a clean filter / the clean filter

So:

• čistý filtr is a noun phrase
• Filtr je čistý is a full sentence

Je is the 3rd person singular present form of být, which means to be.

So:

• já jsem = I am
• ty jsi = you are
• on / ona / ono je = he / she / it is

In Filtr je čistý, je means is.

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

So Filtr je čistý can mean:

• The filter is clean
• A filter is clean

Which one is meant depends on the context. In real use, the situation usually makes it clear.

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

Filtr is masculine singular, so the adjective takes the masculine singular nominative form:

• masculine: čistý
• feminine: čistá
• neuter: čisté
• plural: čisté / čistí, depending on the noun type

So:

• Filtr je čistý. = The filter is clean.
• Voda je čistá. = The water is clean.
• Sklo je čisté. = The glass is clean.

Filtr is a masculine noun, specifically masculine inanimate.

You can often guess masculine gender when a noun ends in a consonant, as filtr does. That is not a perfect rule, but it works very often.

This matters because adjectives and some other words have to match the noun’s gender:

• ten filtr
• čistý filtr
• Filtr je čistý

Filtr is in the nominative singular because it is the subject of the sentence.

čistý is also in the nominative singular because it agrees with the subject after být when used as an adjective.

So the structure is:

• subject: filtr
• verb: je
• predicate adjective: čistý

A simple English-friendly approximation is CHIS-tee, with the stress on the first syllable.

A few details:

• č sounds like ch in church
• i is a short i
• stý has a long ee sound at the end
• Czech stress is almost always on the first syllable: ČIS-tý

Also, in modern Czech, í and ý are pronounced the same. The difference is mainly spelling and grammar, not pronunciation.

Yes, Czech word order is more flexible than English, but different orders sound more or less natural depending on emphasis.

The neutral order is:

• Filtr je čistý.

You might also hear:

• Čistý je filtr. = marked or contrastive, something like It’s the filter that is clean
• Je filtr čistý? = Is the filter clean?

So the basic sentence is the most normal way to say it, but other orders are possible.

Normally, no. In standard Czech, you keep je in a sentence like this.

So you say:

• Filtr je čistý.

not just:

• Filtr čistý.

Omitting je would sound incomplete or very nonstandard in ordinary Czech.

You replace je with není:

• Filtr není čistý. = The filter is not clean.

This is the normal way to negate is in Czech.

The most direct way is:

• Je filtr čistý? = Is the filter clean?

In speech, intonation also helps. Czech does not need a helping verb like English do.

You may also hear a statement-shaped question in conversation, with rising intonation:

• Filtr je čistý?

But Je filtr čistý? is the clearest standard form.

Yes, it is very close in meaning and form. Filtr is the normal Czech word for filter.

Because it looks familiar, it is an easy word for English speakers to remember. Just keep in mind that once it is inside a Czech sentence, it follows Czech grammar:

• filtr
• filtru
• filtrem, etc.

So the meaning is familiar, but the endings change according to Czech rules.