Postea duo passeres super tectum sedent, et puella muscas in horto numerat.

Duo is the masculine nominative plural form of two. It has to agree with passeres in gender, number, and case.

• passeres is masculine
• passeres is plural
• passeres is nominative because it is the subject

So duo passeres means two sparrows.

Passeres is the nominative plural of passer, a third-declension noun.

• singular: passer
• plural: passeres

It is nominative plural here because it is the subject of sedent.

Because its subject is duo passeres, which is plural.
Sedent is the third-person plural present active indicative of sedere, meaning to sit.

So:

• passer sedet = the sparrow sits
• passeres sedent = the sparrows sit

This is a very common Latin question: different prepositions take different cases, and some prepositions can take more than one case depending on meaning.

Here:

• super tectum uses super with the accusative
• in horto uses in with the ablative

For in, the basic rule is:

• in + ablative = location, in/on
• in + accusative = motion into

So:

• in horto = in the garden
• in hortum would mean into the garden

With super, Latin can use either accusative or ablative depending on author and nuance. Here super tectum means on top of / over the roof.

Because super here is followed by the accusative, so tectum is the accusative singular form.

• nominative: tectum
• accusative: tectum
• ablative: tecto

Even though English says on the roof, Latin does not have to use the same case that English speakers might expect.

Because muscas is the direct object of numerat. It is the thing the girl is counting.

• puella = subject
• numerat = verb
• muscas = direct object

The singular is musca and the accusative plural is muscas.

Two things show this:

1. Puella is in the nominative singular, which is the normal case for a subject.
2. Numerat is third-person singular, so it matches a singular subject.

So puella numerat means the girl counts.

Because the sentence describes location, not motion.

• in horto = in the garden
• in hortum = into the garden

A good quick rule is:

• where? → in + ablative
• where to? → in + accusative

Latin word order is more flexible than English word order. English depends heavily on word order to show who is doing what, but Latin often shows that through case endings and verb endings.

So this sentence could be rearranged in various ways without changing the basic meaning, because:

• passeres is clearly the subject
• muscas is clearly the object
• sedent is plural
• numerat is singular

That said, the given order sounds natural and clear:

• time word first: Postea
• then the subject phrase
• then the verb at the end of the clause

Classical Latin does not have articles like English the and a/an. A noun such as puella can mean:

• girl
• a girl
• the girl

The exact sense comes from context.

They can mean either, depending on context.

• sedent can mean sit or are sitting
• numerat can mean counts or is counting

Latin does not normally make the same sharp distinction that English does between counts and is counting.