In peristyliō parvō impluvium lūcidum est, et puella aquam in eō spectat.

Because it is used with in to show location: in the small peristyle.

In Latin, in can take:

• the ablative when it means in/on/at somewhere, with no movement
• the accusative when it means into/onto somewhere, with movement

So:

• in peristyliō parvō = in the small peristyle / in the small courtyard
• not movement into it, just location in it

Also, both words are ablative singular:

• peristyliō = ablative singular of peristylium
• parvō = ablative singular of parvus, matching peristyliō

Because the sentence describes where something is, not motion toward a place.

Compare:

• in peristyliō = in the peristyle / inside the peristyle → location → ablative
• in peristylium = into the peristyle → motion toward → accusative

In this sentence, the impluvium is there. Nothing is moving into the peristyle, so the ablative is correct.

Because impluvium is the subject of est.

The basic structure is:

• impluvium lūcidum est = the clear impluvium is / more naturally, there is a clear impluvium

Since it is the thing that is, it appears in the nominative singular.

Also, impluvium is a neuter noun, and many neuter nominative singular nouns of the second declension end in -um.

Because lūcidum is an adjective agreeing with impluvium.

Latin adjectives must match the noun they describe in:

• gender
• number
• case

Here:

• impluvium is neuter singular nominative
• so the adjective must also be neuter singular nominative
• therefore: lūcidum

So:

• impluvium lūcidum = a clear/bright/shining impluvium

Latin often uses est in a way that English naturally translates as there is or there are.

So:

• impluvium lūcidum est literally looks like a clear impluvium is
• but natural English is there is a clear impluvium

This is very common in Latin. The verb is still just est = is, but English often needs there is to sound natural.

A peristylium is a colonnaded courtyard or open court in a Roman house, usually surrounded by columns.

A native English speaker may not know the word because it is a cultural term, not an everyday Latin noun. In this sentence, it names the place where the impluvium is located.

So in peristyliō parvō means something like:

• in the small peristyle
• in the small colonnaded courtyard

An impluvium is a pool, basin, or sunken area designed to collect rainwater, especially in a Roman house.

It is another specifically Roman architectural word. In a sentence like this, it refers to the water-feature or basin the girl is looking at.

So impluvium lūcidum means:

• a clear basin
• a bright/shining impluvium

depending on the context and translation style.

Because aquam is the direct object of spectat.

The verb spectat means looks at, watches, or observes, and the thing being looked at is put in the accusative:

• puella aquam spectat = the girl looks at the water

So:

• aqua = nominative, water as subject
• aquam = accusative, water as object

Spectat is:

• 3rd person singular
• present tense
• active voice
• indicative mood

from the verb spectāre, meaning to look at, watch, or observe.

So puella aquam in eō spectat means:

• the girl looks at the water in it

Because the subject is singular (puella = the girl), the verb is singular too: spectat = she looks.

Because in eō shows location, so in takes the ablative.

The pronoun here refers back to impluvium, which is:

• neuter
• singular

The forms are:

• id = nominative or accusative neuter singular
• eō = ablative singular

Since the meaning is in it, not into it, the ablative is needed:

• in eō = in it

If the idea were motion into it, you would expect the accusative instead.

Because the pronoun refers back to impluvium, and impluvium is neuter singular.

The pronoun must match its antecedent in gender and number:

• impluvium = neuter singular
• so the pronoun must also be neuter singular

That gives:

• eō = ablative singular masculine/neuter of is, ea, id

It is not ea, because ea would be feminine singular ablative or nominative plural neuter/feminine depending on context. Here the antecedent is neuter singular, so eō is the right form.

It refers to impluvium.

So the sense is:

• the girl looks at the water in it
• that is, the water in the impluvium

Latin often uses a pronoun like this instead of repeating the noun. English does the same:

• There is a basin, and the girl looks at the water in it.

Latin word order is much more flexible than English word order because Latin uses case endings to show how words function.

English depends heavily on position:

• the girl sees the water is not the same as the water sees the girl

Latin can move words around more freely because the endings show what each word is doing:

• puella is nominative, so it is the subject
• aquam is accusative, so it is the object

In this sentence:

• In peristyliō parvō impluvium lūcidum est
• et puella aquam in eō spectat

the order is natural Latin, even though English would usually arrange things differently.

Yes. Depending on context, lūcidus can mean:

• clear
• bright
• shining
• lucid

In a sentence about water or a basin, clear or bright is usually the most natural choice. The exact English word depends on what nuance the translator wants.

So impluvium lūcidum could suggest:

• clear water
• a shining pool
• a bright-looking basin

In a classroom-style restored pronunciation, roughly:

• peristyliō = peh-rih-STY-lee-oh
• impluvium = im-PLOO-wee-um
• lūcidum = LOO-kih-dum

A few useful points:

• y in learned Latin words is pronounced like a Greek-style fronted vowel, but many learners approximate it with i
• c is always hard, like k
• v is often pronounced like w in restored classical pronunciation
• the macron in lūcidum shows the ū is long
• the macron in peristyliō shows the final ō is long

Different teaching traditions pronounce Latin differently, but those details help explain what the spelling is showing.

Because Classical Latin has no articles.

So:

• impluvium can mean an impluvium or the impluvium
• puella can mean a girl or the girl
• aquam can mean water, the water, or sometimes some water, depending on context

English must choose a or the, but Latin leaves that to context. That is why the same Latin sentence can be translated in slightly different ways without changing the grammar.