הכלב נבח וכשכש בזנב.

הכלב means the dog.

The prefix ה־ is the Hebrew definite article, equivalent to English the.

• כלב = dog
• הכלב = the dog

So the noun is definite here: it is talking about the dog, not just a dog.

A natural pronunciation is:

ha-kelev navach ve-khishkesh ba-zanav

A more detailed breakdown:

• הכלב = ha-kelev
• נבח = navach
• וכשכש = ve-khishkesh
• בזנב = ba-zanav

Notes:

• The כ/ח sound in navach and khishkesh is the throaty Hebrew kh sound, like German Bach or Scottish loch.
• In everyday Israeli Hebrew, exact vowels may vary a little by speaker.

נבח is the past tense, 3rd person masculine singular form of the verb לנבוח (to bark).

So:

• נבח = he barked

Because the subject is הכלב (the dog), the masculine singular form is used.

Hebrew past-tense verbs usually show:

• person
• number
• gender

So you do not need a separate word for he here, because the verb form already includes that information.

וכשכש means and wagged.

It is made of two parts:

• ו־ = and
• כשכש = wagged

The base verb is לכשכש, meaning to wag, especially a tail.

So:

• כשכש = he wagged
• וכשכש = and he wagged

In the sentence, the subject is still the dog, so English translates it naturally as and wagged rather than repeating the dog.

Because Hebrew verbs already contain that information.

Both נבח and כשכש are masculine singular past forms, so they already mean:

• he barked
• he wagged

Since הכלב is already stated as the subject, Hebrew does not need to repeat a pronoun like הוא (he).

This is very normal in Hebrew.

This is a very common question.

In Hebrew, the verb לכשכש is commonly used with ב־ before the thing being wagged:

• כשכש בזנב = literally something like wagged with the tail
• natural English: wagged its tail

So even though English says wagged its tail, Hebrew often says כשכש בזנב.

This is just the normal Hebrew pattern with this verb.

By contrast, את is used to mark a definite direct object, but here Hebrew prefers the preposition ב־.

בזנב is made of:

• ב־ = in / with / by
• זנב = tail

But in this sentence, it does not mean literal in the tail.
With כשכש, it means something like with the tail and is understood idiomatically as:

wagged its tail

Also, the noun is definite here:

• ב + הזנב becomes בזנב

So the form includes the idea of the tail.

Hebrew often combines certain prepositions with the definite article ה־.

So:

• ב + הַזנב becomes
• בַּזנב (written without vowels as בזנב)

This is very common in Hebrew.

The same kind of contraction happens with other prepositions too, for example:

• ל + ה־
• כ + ה־

In unpointed everyday writing, you usually just see the combined form, like בזנב.

Not necessarily.

Hebrew often expresses this idea without an explicit possessive ending when the meaning is obvious from context.

Here, since the subject is the dog, כשכש בזנב is naturally understood as:

the dog wagged its tail

Hebrew does have ways to say his tail / its tail more explicitly, but in a sentence like this, the simpler idiomatic form is completely normal.

Because the subject הכלב is grammatically masculine singular.

So the verbs agree with it:

• נבח = masculine singular past
• כשכש = masculine singular past

Hebrew past-tense verbs agree with the subject in gender and number.

If the subject were feminine singular, plural, and so on, the verb forms would change.

Because once the subject is established, Hebrew can simply continue with another verb connected by ו־ (and).

So:

• הכלב נבח וכשכש בזנב

naturally means:

• The dog barked and wagged its tail

Hebrew does not need to say:

• הכלב נבח והכלב כשכש בזנב

That would sound unnecessarily repetitive.

Yes, very normal.

The structure is:

• הכלב = subject
• נבח = first verb
• וכשכש בזנב = second verb phrase

So it is basically:

The dog barked and wagged its tail.

Hebrew word order is flexible, but this is a very natural way to say it.

It comes from the root כשכש, which itself has a repeated shape.

Some Hebrew roots have this kind of repeated consonant pattern, and verbs built from them can sound expressive or vivid. In this case, that fits the idea of repeated tail movement.

So כשכש is just the normal verb for wagged here; it is not an accidental repetition or a typo.