Udział w spotkaniu jest obowiązkowy.

Udział is a very common Polish noun meaning participation, taking part, or sometimes share depending on context.

In this sentence, udział w spotkaniu means participation in the meeting.

A learner may also come across uczestnictwo, which can also mean participation:

• Udział w spotkaniu jest obowiązkowy.
• Uczestnictwo w spotkaniu jest obowiązkowe.

Both are correct, but udział w... is extremely common and natural.

Because the preposition w here means in and requires the locative case when talking about being in or within something.

So:

• basic form: spotkanie = meeting
• after w: w spotkaniu = in the meeting

This is why you do not use spotkanie unchanged here.

A useful pattern is:

• w domu = in the house
• w pracy = at work
• w szkole = at school
• w spotkaniu = in the meeting

Because obowiązkowy is an adjective, and it must agree with the noun it describes.

The noun being described is udział, not spotkanie.

• udział is masculine singular
• so the adjective must also be masculine singular
• therefore: obowiązkowy

Compare:

• Udział jest obowiązkowy. → udział is masculine
• Spotkanie jest obowiązkowe. → spotkanie is neuter

This is a very common point of confusion, because the nearest noun is not always the one controlling agreement.

Udział is in the nominative singular, because it is the subject of the sentence.

The structure is basically:

• Udział w spotkaniu = the subject
• jest = is
• obowiązkowy = mandatory

So the sentence is built like: [Subject] + [is] + [adjective]

In the present tense, Polish often omits jest in informal or condensed style, especially in notices, rules, headlines, or official wording.

So you may see both:

• Udział w spotkaniu jest obowiązkowy.
• Udział w spotkaniu obowiązkowy.

However, the full version with jest is the safest one for learners and sounds completely normal.

Not completely. Polish word order is more flexible than English.

The most neutral version is:

• Udział w spotkaniu jest obowiązkowy.

But other orders are possible for emphasis, for example:

• Obowiązkowy jest udział w spotkaniu.
• W spotkaniu udział jest obowiązkowy. — grammatically possible, but less natural in everyday use

For learners, it is best to use the neutral order first.

Polish does not have articles like a or the.

So spotkanie can mean:

• a meeting
• the meeting

The exact meaning depends on context.

That is why w spotkaniu can be understood as in the meeting if the context already makes it clear which meeting is meant.

Usually, no—not in this sentence.

With udział, Polish normally uses the pattern:

• udział w czymś = participation in something

So:

• udział w spotkaniu is correct

By contrast, na spotkaniu means at the meeting and is used in different structures, for example:

• Byłem na spotkaniu. = I was at the meeting.
• Widzieliśmy się na spotkaniu. = We saw each other at the meeting.

So:

• udział w spotkaniu = correct collocation
• udział na spotkaniu = generally not correct

You simply negate jest with nie:

• Udział w spotkaniu nie jest obowiązkowy.

This means participation in the meeting is not mandatory.

You can also use a different adjective:

• Udział w spotkaniu jest dobrowolny. = participation in the meeting is voluntary

A few helpful points:

• dz in udział sounds like the ds in beds, but said as one unit
• ł sounds like English w
• ą is a nasal vowel; before some consonants it often sounds close to om/on

Very rough pronunciation guides:

• udział ≈ OOD-jyaw
• spotkaniu ≈ spot-KA-nyoo
• obowiązkowy ≈ obov-YONZ-ko-vy

These are only approximations, but they can help at first.

Yes. Depending on style, you might also hear:

• konieczny = necessary
• wymagany = required
• obligatoryjny = obligatory, more formal/bookish
• dobrowolny = voluntary, the opposite

Examples:

• Udział w spotkaniu jest wymagany.
• Udział w spotkaniu jest konieczny.

But obowiązkowy is one of the most straightforward and common choices for mandatory.