Si tempestas in mari est, nautae periculum maximum timent.

Si means if. It introduces the conditional part of the sentence: Si tempestas in mari est = If there is a storm at sea.

This first part is called the if-clause or protasis. The second part, nautae periculum maximum timent, gives the result or consequence.

Tempestas is the subject of the verb est, so it must be in the nominative case.

• tempestas = nominative singular, storm
• tempestatem = accusative singular, which would usually be used as a direct object, not as the subject

So tempestas ... est means a storm ... is or there is a storm.

Because in can take either the ablative or the accusative, depending on the meaning.

• in + ablative = in / on a place, showing location
• in + accusative = into / onto a place, showing movement toward

Here the meaning is location: in the sea / at sea, not motion into the sea. So Latin uses the ablative:

• mare = sea
• mari = ablative singular of mare

So in mari means in the sea or more naturally in English here, at sea.

Mari is the ablative singular of mare, maris, a third-declension neuter noun meaning sea.

Its main forms are:

• nominative singular: mare
• genitive singular: maris
• ablative singular: mari

Because it follows in in a location sense, the ablative is required.

Nautae is in the nominative plural, so it means sailors and serves as the subject of timent.

Latin often puts the subject after the verb or in a different place from English, but here it appears before the object and verb of its clause:

nautae periculum maximum timent = the sailors fear the greatest danger

The verb ending -nt in timent also shows that the subject is they, which matches plural nautae.

Yes. Nauta, nautae belongs to the first declension, but it refers to a male person in traditional Latin usage and is treated as masculine.

This can feel strange to English speakers, because many first-declension nouns are feminine. But some first-declension nouns referring to jobs or roles commonly held by men are masculine, such as:

• nauta = sailor
• agricola = farmer
• poeta = poet

So nautae here means the sailors, and it is grammatically masculine.

Because it is the direct object of timent.

The verb timeo, timere means to fear, and the thing feared is put in the accusative case. So:

• periculum = accusative singular of periculum, danger
• maximum = accusative singular neuter of maximus, greatest / very great, agreeing with periculum

Together, periculum maximum means the greatest danger or very great danger, depending on context.

Because the adjective must agree with the noun it describes.

Periculum is:

• neuter
• singular
• accusative

So the adjective must also be:

• neuter
• singular
• accusative

That gives maximum.

Agreement in Latin means adjectives match their nouns in:

• gender
• number
• case

It can suggest either, depending on context.

Strictly speaking, maximus is the superlative form of magnus, so it often means greatest, largest, or very great. In a sentence like this, English might translate it naturally as:

• the greatest danger
• very great danger
• extreme danger

So a learner should recognize that the superlative often has a slightly flexible translation in English.

Timent is:

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

It comes from timeo, timere, meaning to fear.

So timent means they fear.

Because nautae is plural, the verb must also be plural:

• timet = he/she/it fears
• timent = they fear

Latin often uses the present indicative in both parts of a simple, real condition, especially for a general truth or a straightforward situation.

So:

• Si tempestas in mari est = If there is a storm at sea
• nautae periculum maximum timent = the sailors fear the greatest danger

This is a normal present simple condition: if X happens/is true, Y happens/is true.

Classical Latin does not have definite or indefinite articles like English the and a/an.

So a noun like tempestas can mean:

• a storm
• the storm

and nautae can mean:

• sailors
• the sailors

You decide from the context which English translation is best. That is why the Latin sentence can be translated smoothly even though no article appears.

Yes. Latin word order is much more flexible than English word order because the endings show the grammatical roles.

For example, these would still mean essentially the same thing:

• Si in mari tempestas est, nautae periculum maximum timent.
• Nautae, si tempestas in mari est, periculum maximum timent.
• Si tempestas in mari est, maximum periculum nautae timent.

However, word order can change the emphasis. The original sentence is clear and straightforward, but Latin authors often move words around for style or focus.

In classical prose, est is normally expressed here because it means is in the clause tempestas in mari est.

Latin sometimes omits forms of to be, especially in poetry or very compressed expressions, but in a standard sentence like this, keeping est is normal and expected.

So tempestas in mari est is the full and ordinary way to say there is a storm at sea.