Regina coronam pulchram habet, quam omnes in atrio spectant.

Because regina is in the nominative singular, which is the case normally used for the subject of a finite verb.

• regina = queen
• nominative singular feminine

So Regina ... habet means The queen ... has.

Also, the verb habet is third person singular, which matches a single subject: she has.

In Latin, finite verbs agree with their subject in person and number, but not in gender.

So:

• regina is feminine
• but the verb is simply third person singular
• therefore habet = he/she/it has

The feminine idea comes from regina, not from a special feminine verb form.

Because pulchram describes coronam, and Latin adjectives must agree with the nouns they modify in:

• gender
• number
• case

Here:

• coronam = feminine singular accusative
• pulchram = feminine singular accusative

They are accusative because coronam pulchram is the direct object of habet: the queen has a beautiful crown.

Because it is the direct object of habet.

The verb habere means to have, and the thing possessed is put in the accusative:

• Regina coronam habet = The queen has a crown

So coronam is accusative singular.

Quam is a relative pronoun, here meaning which.

It refers back to coronam. That earlier noun is called its antecedent.

A relative pronoun in Latin works like this:

• its gender and number come from its antecedent
• its case comes from its job inside the relative clause

So here:

• antecedent: coronam = feminine singular
• inside the clause quam omnes in atrio spectant, the pronoun is the direct object of spectant
• therefore it must be accusative singular feminine

That gives quam.

Because the form points that way.

• quam is feminine singular accusative
• coronam is also feminine singular accusative/singular feminine antecedent
• semantically, it also makes better sense: everyone is looking at the crown

If the relative pronoun referred to regina, the sentence structure and meaning would normally make that clearer in some other way. In this sentence, the natural antecedent is coronam.

Because Latin is using omnes, literally all (people), as the subject of spectant.

So grammatically it is plural:

• omnes = all, all people, or idiomatically everyone
• therefore the verb is plural: spectant = they are looking at / they look at

English often uses everyone with a singular verb, but Latin here is expressing the idea with a plural word.

Because its subject is omnes, which is plural.

• omnes ... spectant = all are looking at ...

So:

• spectat would mean he/she/it looks at
• spectant means they look at

Because in takes different cases depending on meaning:

• in + ablative = in/on a place, showing location
• in + accusative = into/onto a place, showing motion toward

Here the sense is location: everyone is looking at the crown in the atrium/hall.

So Latin uses:

• in atrio = in the atrium

If the sentence meant movement into the atrium, then in atrium would be possible.

Yes. Latin spectare commonly takes a direct object in the accusative.

So:

• quam ... spectant = which they are looking at / watching

English often needs look at, but Latin does not always use a preposition in the same way. Many Latin verbs take a direct object where English would use a verb + preposition.

Yes. Latin word order is much more flexible than English word order because case endings show the grammatical relationships.

This sentence has a very normal and readable arrangement:

• Regina — subject first
• coronam pulchram — object with adjective
• habet — verb
• then the relative clause: quam omnes in atrio spectant

But other orders are possible, for example to emphasize different words. Latin often places emphasis by position, especially near the beginning or end of a clause.

So this order is natural, but not the only possible one.

No major change in basic meaning. Latin adjectives can come before or after the noun.

So both of these could mean a beautiful crown:

• coronam pulchram
• pulchram coronam

Sometimes word order adds emphasis or style, but the agreement endings show that pulchram modifies coronam either way.

It is a relative clause modifying coronam.

The main clause is:

• Regina coronam pulchram habet = The queen has a beautiful crown

Then the relative clause adds more information about that crown:

• quam omnes in atrio spectant = which everyone is looking at in the atrium

So the relative clause acts like an adjectival description of coronam.