Si ventus fortis est, ancilla candelam statim extinguit.

Because fortis is a third-declension adjective. It means strong and must agree with ventus in gender, number, and case.

Here, ventus is:

• masculine
• singular
• nominative

The masculine/feminine nominative singular form of fortis is fortis, not fortus. So ventus fortis means a strong wind or the wind is strong depending on context.

Latin often uses est to mean is when making a full statement: the wind is strong.

So:

• ventus fortis = a strong wind / the strong wind as a noun phrase
• ventus fortis est = the wind is strong as a complete clause

In this sentence, est is needed because the clause is stating a condition: if the wind is strong.

Si means if. It introduces the condition.

So the sentence is divided into two parts:

• Si ventus fortis est = If the wind is strong
• ancilla candelam statim extinguit = the maidservant immediately extinguishes the candle

This is a basic conditional sentence using the indicative mood.

Ancilla is in the nominative singular because it is the subject of extinguit.

The nominative case is used for the person or thing doing the action. Here, the maidservant is the one who extinguishes the candle, so ancilla must be nominative.

Because candelam is the direct object of extinguit.

The verb extinguere means to extinguish, and the thing being extinguished is the candle. In Latin, the direct object normally goes in the accusative case.

So:

• candela = nominative singular, the candle as subject
• candelam = accusative singular, the candle as object

Extinguit is:

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

It means he/she/it extinguishes or sometimes does extinguish.

Because the subject is ancilla, it means the maidservant extinguishes.

Latin verbs usually include the subject within the verb ending, so a separate pronoun like she is often unnecessary.

• est = he/she/it is
• extinguit = he/she/it extinguishes

However, Latin can still include a noun subject when needed for clarity. So ancilla extinguit explicitly tells us who performs the action.

English usually needs pronouns, but Latin often does not.

Statim means immediately. Latin word order is more flexible than English, so adverbs can often be placed in different positions.

Here, statim comes before the verb to emphasize the speed of the action:

• ancilla candelam statim extinguit

That is perfectly natural Latin. The meaning would still be basically the same if the word order changed, as long as the forms remain clear.

It is important for style and emphasis more than for basic grammar.

Because Latin uses case endings, the roles of the words are mostly shown by their forms:

• ancilla = subject
• candelam = object

So Latin can move words around more freely than English. For example, these would still mean roughly the same thing:

• Si ventus fortis est, ancilla candelam statim extinguit.
• Si ventus fortis est, statim ancilla candelam extinguit.
• Si ventus fortis est, candelam ancilla statim extinguit.

But the original order is clear and natural.

Because this is a simple, straightforward condition: if the wind is strong.

Latin often uses the indicative in ordinary real or general conditions, especially when the speaker is presenting the condition as a normal possibility or fact.

So:

• si ventus fortis est = if the wind is strong

There is nothing hypothetical, contrary-to-fact, or especially uncertain here that would require the subjunctive.

It can be understood either way, depending on context.

In the present tense, this kind of sentence may mean:

• a general truth or habit: If the wind is strong, the maidservant immediately puts out the candle
• a present situation in a story: If the wind is strong, the maidservant immediately puts out the candle

Latin present tense can cover both ordinary present and habitual present, just as English sometimes does.

The dictionary form is usually given as extinguo, extinguere, extinxi, exstinctum or similar forms depending on spelling conventions.

From that, you can identify:

• extinguo = I extinguish
• extinguere = to extinguish

The form extinguit is the third person singular present active: he/she/it extinguishes.

Latin has no definite article like English the, and no indefinite article like a/an either.

So:

• ventus can mean wind, a wind, or the wind
• ancilla can mean maidservant, a maidservant, or the maidservant
• candelam can mean a candle or the candle

Context tells you which is most natural in translation.

Because ventus is in the nominative singular, and it matches the predicate adjective fortis.

In ventus fortis est:

• ventus = subject
• fortis = predicate adjective describing the subject
• est = linking verb

So the structure is subject + adjective + is: the wind is strong.