Bremsebelegget er tynt.

Because Norwegian usually puts the definite article at the end of the noun.

• et bremsebelegg = a brake pad / a brake lining
• bremsebelegget = the brake pad / the brake lining

The ending -et is the neuter singular definite article. So bremsebelegget already includes the idea of the.

It is a compound noun:

• bremse- = brake
• belegg = lining, coating, pad

So bremsebelegg is literally something like brake lining / brake pad.

A very useful rule in Norwegian is that the last part of a compound decides the gender. Since belegg is neuter, bremsebelegg is also neuter.

Because the noun is neuter singular.

The adjective tynn changes form to match the gender and number of the noun:

• en tynn ... for common-gender singular
• et tynt ... for neuter singular
• tynne ... for plural

Since bremsebelegg is a neuter noun, the sentence uses tynt:

• Bremsebelegget er tynt.

This agreement also happens when the adjective comes after er, not just before the noun.

The dictionary form is tynn.

Common forms are:

• tynn = common-gender singular
• tynt = neuter singular
• tynne = plural, and also the definite form when the adjective comes before a noun

For example:

• en tynn plate
• et tynt lag
• tynne plater

Because in this sentence the adjective is predicative: it comes after er and describes the subject.

In Norwegian, predicative adjectives agree with gender and number, but not with definiteness.

So:

• det tynne bremsebelegget = the thin brake pad
  
  • here the adjective is before the noun, so you use tynne
• bremsebelegget er tynt = the brake pad is thin
  
  • here the adjective is after er, so you use the neuter singular form tynt

That difference is very common in Norwegian.

No. This is a very basic Norwegian sentence pattern:

• Bremsebelegget = subject
• er = verb
• tynt = adjective/complement

So it follows the normal pattern:

subject + verb + complement

If you turn it into a yes/no question, the verb comes first:

• Er bremsebelegget tynt?

A natural plural version is:

• Bremsebeleggene er tynne. = The brake pads are thin.

Here:

• bremsebeleggene = definite plural
• tynne = plural adjective form

The indefinite plural is usually:

• bremsebelegg

So you can compare:

• et bremsebelegg
• bremsebelegget
• bremsebelegg
• bremsebeleggene

That is a normal spelling pattern in Norwegian.

The adjective is tynn, but the neuter ending gives tynt, not tynnt. The same kind of thing happens in some other adjectives too. So this is something you mainly learn as part of the adjective form:

• tynn → tynt

It is not a different word; it is just the neuter form.

Then you would get a different structure:

• det tynne bremsebelegget = the thin brake pad

Notice two things happen:

1. You add det before the noun phrase.
2. The adjective becomes tynne, not tynt.

So compare:

• Bremsebelegget er tynt. = The brake pad is thin.
• det tynne bremsebelegget = the thin brake pad

That is a very useful contrast to learn.