Podwozie jest suche.

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

Here, podwozie is:

• singular
• neuter
• nominative

So the adjective must also be singular neuter nominative: suche.

Compare:

• suchy = masculine
• sucha = feminine
• suche = neuter

So:

• samochód jest suchy = the car is dry
• karoseria jest sucha = the body is dry
• podwozie jest suche = the undercarriage is dry

Podwozie is a neuter noun.

A very common clue is the ending:

• many Polish neuter nouns end in -o, -e, or -ę

So podwozie behaves as a neuter noun, which is why the adjective is suche.

Yes, it is singular.

This is a very common point of confusion for English speakers. In Polish, an ending like -e does not automatically mean plural. Many neuter singular nouns end in -e.

Here:

• podwozie = singular
• podwozia = plural

So Podwozie jest suche means The undercarriage is dry, not The undercarriages are dry.

Jest means is. It is the 3rd person singular present tense of być (to be).

So:

• podwozie = the undercarriage
• jest = is
• suche = dry

Unlike in some other Slavic languages, in normal standard Polish you usually do keep jest in a sentence like this.

In a normal full sentence, no—you would usually say Podwozie jest suche.

You may sometimes see Podwozie suche in:

• notes
• headlines
• technical descriptions
• very clipped speech

But for standard learner Polish, Podwozie jest suche is the correct full version.

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

Suche is also in the nominative, because it is a predicate adjective after być.

This is useful to remember:

• with adjectives after być, Polish normally uses the nominative
• with predicate nouns, Polish often uses the instrumental

For example:

• Podwozie jest suche = adjective, so nominative
• Jan jest mechanikiem = noun, so instrumental

The most neutral word order is:

Podwozie jest suche.

Polish word order is fairly flexible, so other orders are possible, but they change the emphasis.

For example:

• Suche jest podwozie. = puts more focus on dry
• Podwozie suche jest. = possible, but sounds marked or stylistically unusual

So if you are learning the standard pattern, stick with Podwozie jest suche.

A rough English-friendly guide is:

pod-VO-zhye yest SU-he

A few pronunciation notes:

• podwozie: stress on WO
• jest: sounds like yest
• ch in suche is like a hard h sound, not English ch
• suche has two syllables: SU-che

Polish stress is usually on the second-to-last syllable of a word:

• podWOzie
• SUche

Not always. The exact English translation depends on context.

Podwozie can refer to things like:

• undercarriage
• chassis
• landing gear (in aircraft contexts)

So the grammar of the sentence stays the same, but the best English equivalent may change depending on what object you are talking about.