Scelus grave est.

Because scelus is neuter singular, and the adjective has to agree with it.

The adjective is gravis, grave = serious / heavy / severe.
Its nominative singular forms are:

• masculine/feminine: gravis
• neuter: grave

Since scelus is a neuter noun, Latin uses grave.

Here scelus is nominative singular, because it is the subject of est.

With a sentence like X est Y, the thing being described is normally in the nominative, and the describing adjective is also nominative:

• scelus = the subject
• grave = predicate adjective describing the subject

A beginner might notice that scelus could also look like an accusative form, because many neuter nouns have the same form in nominative and accusative. But in this sentence, the verb est shows that scelus is functioning as the subject, so nominative makes sense.

Scelus is a third-declension neuter noun.

Its basic dictionary form is:

• scelus, sceleris = crime, wicked deed, sin, villainy

A useful thing to know is that its stem changes:

• nominative singular: scelus
• stem in the other cases: sceler-

For example:

• genitive singular: sceleris
• dative singular: sceleri
• ablative singular: scelere

That -us ending may look like a second-declension masculine noun at first, but it is not. It is a third-declension neuter noun.

Est is the third-person singular present indicative active of sum, meaning to be.

So est means:

• is

In this sentence, it links the subject scelus with the adjective grave:

• Scelus grave est = The crime is serious / Crime is serious

This is the same kind of structure as:

• Puella laeta est = The girl is happy
• Bellum longum est = The war is long

Latin does not have articles like English the and a/an.

So scelus can mean, depending on context:

• a crime
• the crime
• crime

And Scelus grave est could be understood in different ways depending on the situation, for example:

• The crime is serious
• A crime is serious
• Crime is serious
• This crime is serious (if context makes that clear)

English has to choose an article, but Latin often leaves that to context.

Yes. Latin word order is much more flexible than English word order.

This sentence could also appear as:

• Scelus est grave
• Grave scelus est
• Grave est scelus

They all mean roughly the same thing, though the emphasis may shift a little.

In Scelus grave est, the order is straightforward:

• subject: scelus
• adjective: grave
• verb: est

Latin often places the verb at or near the end, so this order feels very natural.

It is an adjective, but specifically it is being used as a predicate adjective.

That means it is not directly attached to the noun inside a noun phrase like grave scelus = a serious crime.
Instead, it is linked to the noun by est:

• grave scelus = a serious crime
• scelus grave est = the crime is serious

So in this sentence, grave is describing the subject through the verb est.

Originally, gravis, grave can mean heavy, but in many contexts it also means:

• serious
• severe
• important
• burdensome
• weighty

In Scelus grave est, the natural sense is serious or grave in English.

So yes, the adjective has a literal meaning related to weight, but here it is being used in a moral or abstract sense.

Yes. Scelus can mean more than just a legal crime.

Depending on context, it can refer to:

• a crime
• a wicked act
• an evil deed
• villainy
• sin or outrage

So the sentence may carry a stronger moral tone than a simple legal statement. It can suggest not just lawbreaking, but real wickedness.

Because Latin verbs already contain person and number in their endings.

Est by itself already means he/she/it is. So Latin does not need to add a separate subject pronoun unless it wants emphasis.

In this sentence, the subject is explicitly given as scelus, so no pronoun is needed anyway:

• Scelus grave est = The crime is serious

If there were no noun, est could still mean it is, depending on context.

A good beginner strategy is:

1. Find the verb: est = is
2. Find the nominative subject: scelus
3. Match the agreeing adjective: grave

So the structure is:

• scelus = subject
• grave = adjective agreeing with the subject
• est = linking verb

That gives you the basic pattern:

subject + predicate adjective + verb

This is a very common Latin sentence type, so it is a useful model to learn early.