Cave aquam in pavimentō relinquās, sī ventus per compluvium nimis fortis intrat.

Cave is the singular imperative of cavēre, meaning beware, take care, or in this kind of sentence simply don’t.

So Cave aquam ... relinquās is a warning addressed to one person: Be careful not to leave water... or more naturally Don’t leave water...

If you were speaking to more than one person, Latin would use cavēte.

After cave, Latin often uses the present subjunctive to express a warning or prohibition.

So:

cave relinquās = be careful not to leave / don’t leave

This is a standard Latin construction. You may also see cave nē relinquās, with nē added, but Latin can omit nē after cave.

Aquam is the direct object of relinquās.

The verb relinquere means to leave behind, and what is being left is water. Because it is the direct object, Latin puts it in the accusative case:

• nominative: aqua = water
• accusative: aquam = water as the thing affected by the verb

With in, Latin uses:

• accusative for motion into / onto
• ablative for location in / on

Here the idea is not movement onto the floor, but location: the water is being left on the floor. So Latin uses the ablative:

in pavimentō = on the floor / on the pavement-surface

If the sentence meant pour water onto the floor, then the accusative would be more likely.

Not exactly. Pavimentum can mean a paved surface, but in many contexts it means a floor, especially an indoor floor.

So in this sentence, an English learner should not automatically think of a sidewalk. It is more likely talking about the floor of a house or room.

Here compluvium is accusative singular because it follows per, and per takes the accusative case.

So:

• per compluvium = through the compluvium

The compluvium was the opening in the roof of an atrium through which rainwater and air could come in.

A compluvium is a specifically Roman architectural feature: the opening in the roof of the atrium.

It allowed light, air, and rainwater to enter. The rainwater would typically fall into the impluvium, the basin below.

So per compluvium is not just through a skylight in a modern sense; it refers to a recognizable part of a Roman house.

Because fortis is an adjective describing ventus.

• ventus = the wind
• fortis = strong

So ventus ... nimis fortis means the wind is too strong.

English might express the whole idea more idiomatically as if the wind comes in too strongly through the compluvium, but the Latin is built around the noun wind being too strong, not around the verb being modified by an adverb.

Because the sī clause here is a normal, real condition:

sī ventus ... intrat = if the wind comes in...

Latin commonly uses the indicative in straightforward if clauses when the condition is presented as real or possible in an ordinary way.

So there is nothing unusual about sī + intrat here.

Latin usually does not need to state subject pronouns, because the verb ending already shows the person and number.

Relinquās means you leave in the sense of you may leave / you are to leave within this construction, and the ending -ās shows second person singular.

So Latin can leave out tū unless it wants emphasis.

It is more flexible than English, but not especially strange for Latin.

A rough breakdown is:

Cave | aquam | in pavimentō | relinquās,
sī | ventus | per compluvium | nimis fortis | intrat.

A few things to notice:

• Cave comes first because it gives the warning immediately.
• aquam appears early because it is the important thing not to leave.
• The sī clause comes after the main warning.
• nimis fortis is placed near ventus because it describes the wind.

Latin often arranges words for emphasis and clarity rather than following a fixed English-style order.