In die sollemni mater coronas in atrio ponit.

Because Latin uses in in more than one way.

• in die sollemni = a time expression, on the festival day
• in atrio = a place expression, in the atrium

So the same preposition appears twice, but it is introducing two different kinds of information: when and where.

Die is the ablative singular of dies, diei, meaning day.

This noun belongs to the fifth declension, which is why its forms may look unfamiliar if you are used to first- and second-declension endings.

A quick summary:

• nominative singular: dies
• accusative singular: diem
• ablative singular: die

Here the sentence needs the ablative, so we get die.

Sollemni agrees with die.

That means it matches die in:

• case: ablative
• number: singular
• gender: masculine here

So die sollemni means on the festival day or on the solemn/festive day.

This is a standard Latin pattern: adjectives must agree with the nouns they modify.

In Latin, the subject is identified mainly by its case, not by its position.

Mater is nominative singular, so it is the subject: mother.

English usually depends much more on word order, but Latin is freer because the endings show the grammatical role. So even though mater comes after in die sollemni, it is still the subject.

Also, mater is a third-declension noun, so it does not have the very common first-declension feminine ending -a. Not all feminine nouns look like puella.

Because coronas is the direct object of ponit.

The mother is placing the wreaths/garlands/crowns, so those are the things directly affected by the action. In Latin, the direct object normally goes in the accusative case.

Corona is a first-declension noun, so:

• nominative singular: corona
• accusative singular: coronam
• accusative plural: coronas

That is why the sentence has coronas.

Atrio is ablative singular after in.

Here in atrio gives the place associated with the action: in the atrium.

So:

• atrium = nominative/accusative singular
• atrio = ablative singular

With in, the ablative commonly expresses location. That is why you see in atrio.

Ponit is:

• third person
• singular
• present tense
• active
• indicative

It comes from pono, ponere, meaning to put, to place, or to set.

So ponit means she puts/places or mother puts/places.

Notice that Latin does not need a separate word for she here, because the ending -t already tells you the subject is he/she/it singular.

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

A very common Latin pattern is to place the verb near or at the end of the sentence. Here that gives a natural Latin flow:

• In die sollemni = sets the scene in time
• mater = gives the subject
• coronas = gives the object
• in atrio = gives the place
• ponit = finishes with the action

English often prefers a stricter order, but Latin can move words around for emphasis without changing the basic meaning, since the endings already show each word’s role.

Yes, to a large extent.

Because Latin uses case endings, several word orders are possible without changing the core meaning. For example, Latin could move mater, coronas, or in atrio to different positions for emphasis.

What changes most is usually the focus or style, not the basic grammar.

In this version, starting with In die sollemni highlights the time first, almost like setting the scene: On the festival day...