To jest wyjątek.

• to = this / that / it in a very general pointing or identifying sense
• jest = is
• wyjątek = exception

So the structure is literally This/That/It is an exception.

In Polish, to is very often used in sentences where you identify or label something:

• To jest dom.
• To moja siostra.
• To problem.
• To jest wyjątek.

Here, to does not have to match the gender of wyjątek. It works more like a general this/that/it used for identification.

That is a very common question.

In Polish, after to (jest) in identifying sentences, the noun is usually in the nominative case:

• To jest wyjątek.
• To jest lekarz.
• To jest mój brat.

But after a normal subject + jest, Polish often uses the instrumental for the predicate noun:

• Ten przypadek jest wyjątkiem.
• Jan jest lekarzem.

So:

• To jest wyjątek. = identifying something
• Ten przypadek jest wyjątkiem. = saying that a particular case is an exception

Both are correct, but the grammar pattern is different.

Yes. To wyjątek is natural and common, especially in speech.

• To jest wyjątek. = full, neutral
• To wyjątek. = slightly shorter, very common

As a learner, To jest wyjątek is the safest full form, but you will definitely hear To wyjątek too.

Roughly: vih-YON-tek

A few helpful details:

• w sounds like English v
• y is a Polish vowel that does not sound exactly like English ee
• j sounds like English y
• ą before t is usually pronounced something like on
• stress falls on the second-to-last syllable: wy-JĄ-tek

So the stress is on ją.

Wyjątek is a masculine inanimate noun.

You can often tell it is masculine because the singular nominative form ends in a consonant.

That matters when you use adjectives or other words with it, for example:

• ten wyjątek = this exception
• mały wyjątek = a small exception

But in To jest wyjątek, you still use to, not ten, because to here is part of the identifying structure.

Yes, but some versions are more natural than others.

Most common:

• To jest wyjątek.
• To wyjątek.

Also possible:

• Jest to wyjątek. — a bit more formal or written

Polish word order is flexible, but for a beginner, To jest wyjątek is the best standard pattern.

Negative:

• To nie jest wyjątek.

Question:

• Czy to jest wyjątek?
• To jest wyjątek? — possible in speech, with question intonation

So czy is a common way to make a yes/no question in Polish.

The plural is wyjątki.

Examples:

• To są wyjątki. = These are exceptions.
• Wyjątki się zdarzają. = Exceptions happen.

A few useful forms:

• singular nominative: wyjątek
• singular instrumental: wyjątkiem
• plural nominative: wyjątki

Not always. Depending on context, to jest can be:

• this is
• that is
• it is

Polish to is broader than English this. In many real situations, you choose the best English translation from the context, but the Polish sentence itself stays the same:

• To jest wyjątek.
  could be This is an exception, That is an exception, or It is an exception, depending on what you are talking about.