Specus sub terra iacet.

Because specus is in the nominative singular, which is the case normally used for the subject of a Latin sentence.

In Specus sub terra iacet, the thing doing the lying is the cave, so specus is the subject.

A learner may expect a more familiar ending like -a or -us from first- or second-declension nouns, but specus is a fourth-declension noun, and its nominative singular happens to look like this.

Terra is ablative singular.

It follows the preposition sub, and here sub means under in the sense of location rather than motion. With this meaning, Latin commonly uses sub + ablative.

So:

• sub terra = under the ground / beneath the earth

Because Latin often distinguishes:

• place where something is → ablative
• motion toward a place → accusative

So:

• sub terra iacet = it lies under the ground → location → ablative
• sub terram it = it goes under the ground → motion toward → accusative

In this sentence, the cave is not moving anywhere; it is simply located there, so terra is ablative.

Iacet is the third person singular present active indicative of iaceo.

In this sentence it means something like:

• lies
• rests
• is situated

So it does not necessarily mean that the cave is physically lying down in the way a person lies down. It is a normal Latin way to say that something is located somewhere.

Because the subject, specus, is singular.

Latin verbs agree with their subjects in person and number. Since specus means a cave or the cave, the verb must be singular:

• specus ... iacet = the cave ... lies

If the subject were plural, the verb would be plural too.

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

Putting the verb at the end is very common in Latin, especially in simpler or more neutral sentences. So Specus sub terra iacet is a very natural order.

But other orders could also be grammatical, for example:

• Sub terra specus iacet
• Specus iacet sub terra

The basic meaning would stay the same, though the emphasis might shift slightly.

No. Latin has no definite article like English the, and no indefinite article like a or an.

So specus can mean:

• a cave
• the cave

and terra can mean:

• earth
• the ground
• the earth

You understand the exact sense from context.

Specus is a fourth-declension noun, usually masculine.

That matters because fourth-declension nouns do not follow the more familiar first- or second-declension patterns many beginners learn first.

For example, its dictionary form is typically:

• specus, specūs = cave, grotto, cavern

So in this sentence, specus is nominative singular.

Yes. Sub can take either the ablative or the accusative.

A helpful rule is:

• sub + ablative = under in the sense of being in a place
• sub + accusative = under in the sense of movement toward a place

That is why sub terra here shows location, not motion.

In a classical-style pronunciation, it would be approximately:

SPEH-koos soob TEHR-rah YAH-ket

A few helpful points:

• c is always hard, like k
• i before another vowel in iacet sounds like y
• ae would sound like eye, but there is no ae in this sentence
• terra has a doubled r, so the r is held a little longer

Yes. Even if the basic meaning is already clear, English can phrase it in several natural ways, such as:

• The cave lies under the ground.
• The cave is beneath the earth.
• The cave is underground.
• A cave lies under the ground.

Latin often leaves choices like the versus a and exact wording to the context.

Yes.

The preposition is sub, and its object is terra. Together they form the prepositional phrase sub terra, which tells you where the cave lies.

So the sentence breaks down like this:

• Specus = subject
• sub terra = prepositional phrase showing location
• iacet = verb

Because Latin relies heavily on inflected endings.

In English, word order does much of the work:

• The cave lies under the ground is normal
• changing the order can confuse the meaning

In Latin, the endings already tell you the roles:

• specus = nominative subject
• terra = ablative after sub
• iacet = singular verb

So Latin can move the words around more freely without losing clarity.