Quam bene histrio gesticulatur!

Here quam is exclamatory, not comparative.

In this sentence, quam bene means how well!

So quam is being used the same way English uses how in an exclamation:

• How well the actor gestures!

This is different from other common uses of quam, such as:

• than
• how much
• as ... as

Latin often uses quam + an adjective or adverb to make an exclamation.

Because bene is an adverb, while bonus is an adjective.

• bonus = good
• bene = well

Since the word is describing how the actor gestures, Latin needs an adverb:

• gesticulatur = gestures
• bene = well

So bene modifies the verb, not the noun.

Histrio is nominative singular, so it is the subject of the sentence.

The verb gesticulatur is 3rd person singular, so it matches a singular subject:

• histrio = the actor
• gesticulatur = gestures / is gesturing

Even though English usually puts the subject first, Latin does not have to. The subject can come after quam bene without causing confusion, because the case ending and the verb form make the role clear.

Yes, it looks passive, but this verb is deponent.

The dictionary form is:

• gesticulor, gesticulari = to gesture

Deponent verbs use passive-looking forms but have active meanings.

So:

• gesticulatur literally looks like a passive form
• but it means he/she gestures, not he/she is gestured

This is a very common thing in Latin, and it often surprises English speakers.

It is present tense, indicative mood, 3rd person singular.

So it can mean:

• the actor gestures
• the actor is gesturing

Which English translation sounds best depends on context. In an exclamation like this, English often prefers is gesturing, but Latin simply uses the present tense.

Latin word order is much more flexible than English word order.

Here quam bene comes first for emphasis. The speaker is reacting strongly to the quality of the action:

• How well...!

Then comes the subject:

• histrio = the actor

And then the verb:

• gesticulatur = gestures

So the order highlights the exclamation first. Latin often moves the most important or emotionally charged part to the beginning.

Yes. Latin could rearrange the words, for example:

• Histrio quam bene gesticulatur!
• Gesticulatur quam bene histrio!

But the original order is especially natural if the speaker wants to emphasize how well he gestures.

Different word orders do not usually change the basic meaning, but they can shift the emphasis.

No. Here it is an exclamation.

The exclamation mark shows that the speaker is expressing admiration or surprise:

• Quam bene histrio gesticulatur! = How well the actor gestures!

If it had a question mark instead, it could be read as an actual question in some contexts, but here the punctuation and tone make it clearly exclamatory.

Histrio is a 3rd-declension noun.

Its basic forms are:

• histrio = nominative singular
• histrionis = genitive singular

That means it does not follow the -us / -i pattern of many masculine nouns. A learner might expect an actor to be something like actor or a second-declension noun, but histrio belongs to the third declension instead.

No. Latin does not use a helping verb like English does in this kind of sentence.

English can say:

• The actor gestures well
• The actor does gesture well

Latin simply uses the single verb gesticulatur. The emphasis comes from word order and from quam bene, not from an extra auxiliary verb.