De hond blaft alsof hij waaks is.

Because hond is a de-word in Dutch. Dutch singular nouns take either de or het, and hond belongs to the de group.

Useful comparisons:

• de hond = the dog
• de honden = the dogs
• het hondje = the little dog / doggy

That last one uses het because diminutives in -je are always het words.

Blaft is the present tense, third-person singular form of blaffen, meaning to bark.

The pattern is:

• infinitive: blaffen
• stem: blaf
• third-person singular: blaf + t = blaft

So:

• ik blaf = I bark
• jij blaft = you bark
• hij/zij/de hond blaft = he/she/the dog barks

Alsof means as if or as though.

So in this sentence, alsof introduces the idea of appearance or comparison:

• De hond blaft alsof hij waaks is = The dog is barking as if he is watchful/on guard.

Dutch uses alsof for this meaning, not plain als.

Compare:

• als = if, when, as, than
• alsof = as if

So alsof is the correct choice here.

Because alsof introduces a subordinate clause, and in Dutch subordinate clauses the conjugated verb usually goes to the end.

So:

• independent clause: Hij is waaks
• subordinate clause: alsof hij waaks is

This is one of the most important Dutch word-order patterns to get used to.

Structure here:

• De hond blaft = main clause
• alsof hij waaks is = subordinate clause

Waaks means something like watchful, alert, guarding, or inclined to keep watch.

It is especially common for dogs. A waakse hond is a dog that notices strangers quickly, guards the house, or acts like a watchdog.

So waaks is not just generally awake or careful. It has a strong sense of being on guard, especially in an animal-like or watchdog-like way.

Because waaks comes after is, so it is being used as a predicative adjective. Predicative adjectives normally do not take -e in Dutch.

Compare:

• De hond is waaks = The dog is watchful
• een waakse hond = a watchful dog

So:

• after a linking verb like zijn: usually no -e
• before a noun: often -e

Yes, zij/ze is possible if the dog is female.

In this sentence, hij is a normal default choice. That can happen because:

• hond is a de-word
• animals are often referred to with hij unless their sex is known or relevant
• for a specific female dog, many speakers would naturally say zij/ze

So all of these are possible depending on context:

• alsof hij waaks is
• alsof ze waaks is

Yes, but the nuance changes a bit.

• waaks is especially natural for dogs and has a watchdog feel.
• waakzaam means vigilant or watchful more generally.

So:

• De hond blaft alsof hij waaks is sounds very dog-specific and natural.
• De hond blaft alsof hij waakzaam is is also understandable, but a little more general or formal in tone.

If you are talking specifically about a dog acting like a guard dog, waaks is a very good choice.

Usually no. Dutch normally does not require a special subjunctive form here.

So present-time Dutch often just uses the ordinary present tense:

• alsof hij waaks is

You can also find past tense in some contexts:

• alsof hij waaks was

That can sound more hypothetical, more distanced, or simply match a past-time context. But Dutch does not have a mandatory special form like English were in as if he were.

Not necessarily. In a short sentence like this, leaving out the comma is completely normal:

• De hond blaft alsof hij waaks is.

A comma may appear in longer sentences or when a writer wants an extra pause, but here the version without a comma is standard and natural.