Der Ärmel meines Mantels ist nass, und der Kragen fühlt sich kalt an.

Because this is the genitive case, which is often used to show possession or a part–whole relationship.

• der Ärmel meines Mantels = the sleeve of my coat
• Literally: the sleeve of my coat

Here, der Ärmel is a part of mein Mantel, so German uses the genitive:

• mein Mantel → nominative
• meines Mantels → genitive

This is a very common pattern in German:

• die Tür des Hauses = the door of the house
• die Farbe des Autos = the color of the car

Because masculine and neuter nouns usually add -s or -es in the genitive singular.

So:

• der Mantel → des Mantels
• with mein: meines Mantels

This -s marks the genitive on the noun itself.

A few more examples:

• der Hund → des Hundes / des Hunds
• das Buch → des Buches
• der Kragen des Mantels = the collar of the coat

Because mein has to change form to match genitive masculine singular.

The noun Mantel is:

• masculine: der Mantel
• singular
• genitive here

So mein becomes meines.

Compare:

• mein Mantel = my coat
• der Ärmel meines Mantels = the sleeve of my coat

This is similar to how articles change:

• der Mantel
• des Mantels

And possessive words change in a parallel way:

• mein Mantel
• meines Mantels

Because both nouns are masculine singular:

• der Ärmel = the sleeve
• der Kragen = the collar

In the sentence, each is the subject of its clause:

• Der Ärmel meines Mantels ist nass
• der Kragen fühlt sich kalt an

So both are in the nominative, and masculine nominative singular takes der.

These are two different ways of describing something:

1. ist nass = states an objective condition

   • The sleeve is wet

2. fühlt sich kalt an = describes how something feels

   • The collar feels cold

So:

• nass sein = to be wet
• sich kalt anfühlen = to feel cold

You usually would not say:

• Der Kragen ist kalt if you specifically want to emphasize the sensation on touch, though it is grammatically possible.

So the second clause focuses on perception.

Sich anfühlen means to feel in the sense of to feel like / to feel to the touch.

It is a separable verb:

• infinitive: sich anfühlen

In a normal main clause, the prefix separates:

• Der Kragen fühlt sich kalt an.

So:

• fühlt goes to the usual verb position
• an moves to the end

Compare:

• Es fühlt sich gut an.
• Die Decke fühlt sich weich an.

In the infinitive, they stay together:

• Der Kragen scheint sich kalt anzufühlen.

Because the verb is used reflexively in German: sich anfühlen.

English says:

• The collar feels cold

German says:

• Der Kragen fühlt sich kalt an

The sich is simply part of how this verb works. It does not mean the collar is literally doing something to itself in an everyday logical sense; it is just the standard German construction.

You will see this with many subjects, not just people:

• Das Wasser fühlt sich warm an.
• Der Stoff fühlt sich weich an.

Because they are predicative adjectives, not adjectives directly in front of a noun.

Compare:

Predicative use:

• Der Ärmel ist nass.
• Der Kragen fühlt sich kalt an.

Here, the adjectives come after ist or with anfühlen, so they do not take endings.

But before a noun, they would take endings:

• der nasse Ärmel
• der kalte Kragen

So:

• der Ärmel ist nass
• der nasse Ärmel

That distinction is very important in German.

Yes, you could say that, and it would be understood.

• der Ärmel meines Mantels = more standard, compact, and often more natural in written German
• der Ärmel von meinem Mantel = common in spoken German

So both are possible, but the genitive version is especially useful to know because it is very common in careful standard German.

This follows normal main-clause word order in German:

1. Der Kragen = subject
2. fühlt = conjugated verb in second position
3. sich = reflexive pronoun
4. kalt = adjective/complement
5. an = separated prefix at the end

So the structure is:

Subject + finite verb + reflexive pronoun + complement + separable prefix

This is a very typical pattern with separable verbs.

Because und joins two full clauses:

• Der Ärmel meines Mantels ist nass
• der Kragen fühlt sich kalt an

Each clause has its own subject, so the second clause also needs its own article:

• der Kragen

You cannot omit it here in normal German.

The ä is an umlauted vowel, and it changes the sound from plain a.

A rough English approximation of Ärmel is something like AIR-mel, though not exactly.

A few useful points:

• Ärmel starts with a vowel sound, so the r follows it closely.
• The ä is not the same as the a in Mantel.
• Mantel sounds more like MAHN-tel than MEN-tel.

It is worth listening to native audio for both words, because vowel quality is one of the trickier parts of German pronunciation for English speakers.