Das Halsband der Hündin ist rot und sehr leicht.

Halsband is a neuter noun in German, so its nominative singular article is das.

• der = masculine
• die = feminine
• das = neuter

Here, das Halsband is the subject of the sentence, so it uses the nominative case.

Because der Hündin is in the genitive case, which is often used to show possession.

So:

• die Hündin = the female dog when it is the subject or in the basic dictionary form
• der Hündin = of the female dog

In this sentence, das Halsband der Hündin means the collar of the female dog, or more naturally in English, the female dog’s collar.

Yes, very often it is.

• das Halsband der Hündin = the female dog’s collar
• literally: the collar of the female dog

German often uses this genitive structure where English would use ’s.

German often forms a specifically feminine noun by adding -in to a masculine noun.

• der Hund = dog / male dog
• die Hündin = female dog

Notice that the vowel changes too:

• Hund → Hündin

That ü is part of the word form, not a separate ending.

Ist is the 3rd person singular form of sein (to be).

It matches the subject das Halsband, which is singular:

• das Halsband ist = the collar is

Even though der Hündin appears near it, that phrase is not the subject. The subject is only das Halsband.

Because after sein (to be), adjectives are usually used as predicate adjectives, and predicate adjectives do not take adjective endings.

So:

• Das Halsband ist rot.
• Das Halsband ist leicht.

But before a noun, adjective endings are required:

• das rote Halsband
• ein leichtes Halsband

So the difference is:

• das rote Halsband = adjective before the noun
• das Halsband ist rot = adjective after sein

Here, leicht means light in weight, not easy.

German leicht can mean different things depending on context:

• ein leichtes Buch = a light book
• eine leichte Aufgabe = an easy task

Because the sentence is talking about a collar, leicht is understood as not heavy.

Because sehr is modifying only leicht in this sentence.

So the meaning is:

• the collar is red
• and very light

It does not say that it is very red.

If you wanted very to apply to both adjectives, you could say:

• Das Halsband ist sehr rot und sehr leicht.

Or in some contexts:

• Das Halsband ist sehr rot und leicht.

But as written, sehr most naturally goes with leicht only.

The sentence follows a very common German pattern:

Subject + verb + complement

Here that is:

• Das Halsband der Hündin = subject noun phrase
• ist = verb
• rot und sehr leicht = predicate/complement

Inside the subject, der Hündin comes after das Halsband because it belongs to it and shows possession:

• das Halsband der Hündin = the female dog’s collar

So the structure is very normal German word order.

A simple guide:

• Hün- sounds roughly like a short German ü, which English does not have exactly
• -din sounds like din

A rough approximation for English speakers is something like HUEN-din, but that is only approximate.

To make ü, try saying ee with your tongue, but round your lips as if saying oo.

Yes, you can, and it would be understood. It means roughly the same thing:

• das Halsband der Hündin
• das Halsband von der Hündin

But der Hündin is the more standard written genitive form here.
The von structure is common in everyday speech, but in a sentence like this, the genitive version sounds more natural and more elegant.

Because German very often forms compound nouns by joining words together.

• Hals = neck
• Band = band, strap, ribbon

So Halsband literally means something like neck-band, which is the normal German word for collar.

This is extremely common in German, and compounds are usually written as one word.