Post scholam puellae ad fontem prope collem ambulant, quia ibi aqua purissima est.

In Latin, post is a preposition that means after, and it takes the accusative case. That is why schola becomes scholam.

• post = after
• scholam = school (accusative singular)

So post scholam literally means after school.

Because post requires the accusative. The basic dictionary form is schola, but after post it must change to scholam.

This is a very common thing in Latin: prepositions often require a specific case.

Here puellae means the girls, so it is nominative plural. It is the subject of ambulant.

• puella = girl
• puellae = girls

Since the verb is plural (ambulant = they walk), the subject also has to be plural.

Puellae can mean more than one thing depending on context:

• nominative plural = girls
• genitive singular = of the girl
• dative singular = to/for the girl

In this sentence, puellae is clearly the subject because it matches the plural verb ambulant. So here it must mean the girls.

Ad means to or toward, and it takes the accusative case. So fons becomes fontem.

• ad = to, toward
• fontem = fountain/spring (accusative singular)

So ad fontem ambulant means they walk to the spring/fountain.

Fons, fontis can mean spring, source, or fountain, depending on context. In a sentence like this, spring is often the most natural meaning, especially because the next clause talks about very pure water.

So ad fontem may suggest to the spring more than to the fountain, though either can work depending on the story.

Prope means near and takes the accusative case. That is why collis becomes collem.

• prope = near
• collem = hill (accusative singular)

So prope collem means near the hill.

They do two different jobs:

• ad fontem tells you where the girls are going
• prope collem tells you where the spring/fountain is located

So the sentence means they are walking to the spring, and that spring is near the hill.

Latin word order is much freer than English word order because Latin uses case endings to show grammatical function. Verbs often come at or near the end of a clause, but they do not have to.

So:

• Post scholam puellae ad fontem prope collem ambulant

is a very natural Latin order.

English depends much more on word order, but Latin does not.

Its basic meaning is they walk. In context, English might sometimes translate it more naturally as they go, but the literal idea is walking.

• ambulat = he/she walks
• ambulant = they walk

So the Latin gives a more specific picture than English go would.

Quia means because. It introduces the reason why the girls walk to the spring.

So the sentence structure is:

• main clause: Post scholam puellae ad fontem prope collem ambulant
• reason clause: quia ibi aqua purissima est

In other words: they go there because the water there is very pure.

Ibi means there. It refers to the place just mentioned: the spring near the hill.

So quia ibi aqua purissima est means:

• because there the water is very pure
• more natural English: because the water there is very pure

Latin often places short adverbs like ibi near the start of the clause.

Because aqua is the subject of est.

• aqua = water (nominative singular)
• purissima = very pure / purest (nominative singular feminine)
• est = is

Since aqua is feminine singular nominative, purissima must match it in gender, number, and case.

Purissima is the superlative form of pura.

• purus / pura / purum = pure
• purior = purer
• purissimus / purissima / purissimum = purest, very pure

So aqua purissima est can mean:

• the water is purest
• more naturally in English: the water is very pure or extremely pure

English often uses very + adjective where Latin uses a superlative.

Because est belongs to the second clause, where the subject is aqua, not puellae.

• puellae ... ambulant = the girls walk
• aqua ... est = the water is

Each clause has its own subject and verb.

Latin has no articles. It does not have separate words for the or a/an.

So:

• puellae can mean girls or the girls
• fontem can mean a spring/fountain or the spring/fountain
• aqua can mean water or the water

You decide from context what sounds best in English.

A very literal version would be:

After school the girls to the spring near the hill walk, because there water very pure is.

That sounds unnatural in English, but it helps show the Latin structure. A more natural English translation rearranges the words:

After school, the girls walk to the spring near the hill, because the water there is very pure.

It is most naturally understood with fontem: the spring near the hill. That is because it comes right after fontem, and semantically it makes good sense.

So the idea is not mainly the girls near the hill walk, but rather the girls walk to the spring that is near the hill.

Here is the breakdown:

• scholam — accusative singular, after post
• puellae — nominative plural, subject of ambulant
• fontem — accusative singular, after ad
• collem — accusative singular, after prope
• aqua — nominative singular, subject of est

This is a good example of how Latin uses case endings to show each noun's role.

Yes. It contains several very common beginner features:

• prepositions with the accusative (post scholam, ad fontem, prope collem)
• a clear nominative subject (puellae)
• a present-tense verb (ambulant)
• a subordinate clause with quia
• adjective agreement (aqua purissima)

So it is a very useful sentence for practicing basic Latin grammar.