Lucia diligentior est quam Marcus, quia menda sua statim corrigit.

Because diligentior is the comparative form of the adjective diligens (careful, diligent).

• diligens = diligent / careful
• diligentior = more diligent / more careful

Since the sentence compares Lucia with Marcus, Latin uses the comparative:

• Lucia diligentior est quam Marcus = Lucia is more diligent than Marcus

In Latin, many comparative adjectives use the same nominative singular form for masculine and feminine.

So:

• masculine: diligentior
• feminine: diligentior
• neuter: diligentius

That means Lucia diligentior est is exactly what we expect for a feminine subject.

Quam means than in comparisons.

So:

• diligentior ... quam Marcus = more diligent than Marcus

It connects the two things being compared:

• Lucia
• Marcus

This is one very common Latin way to make a comparison:

• comparative adjective + quam

Because with quam, Latin normally puts the second item of the comparison in the same case as the first.

Here, Lucia is the subject, so it is nominative. Therefore Marcus is also nominative:

• Lucia ... quam Marcus

So the structure is essentially:

• Lucia is more diligent than Marcus is diligent

That is why Marcus, not Marco, appears here.

Yes. Latin often has two comparison patterns:

1. comparative + quam

   • Lucia diligentior est quam Marcus

2. comparative + ablative

   • Lucia diligentior est Marco

Both can mean Lucia is more diligent than Marcus.

For a learner, the version with quam is often easier to recognize because it looks more like English.

Quia means because.

It introduces a clause that gives the reason for the statement in the first part of the sentence:

• Lucia diligentior est quam Marcus
• quia menda sua statim corrigit

So the second clause explains why Lucia is more diligent:

• because she corrects her mistakes immediately

Menda is the direct object of corrigit (corrects), so it is accusative plural.

The noun is mendum, a neuter noun. Its plural forms are:

• nominative plural: menda
• accusative plural: menda

Because neuter plural nominative and accusative are the same, the form menda could be either by shape alone. Here, its job in the sentence shows that it is accusative:

• she corrects mistakes

Because sua is the reflexive possessive adjective. It refers back to the subject of its own clause.

In quia menda sua statim corrigit, the subject is understood to be Lucia, so:

• sua = her own

Thus:

• menda sua = her own mistakes

If Latin used eius, that would usually mean his/her mistakes belonging to someone else, not the subject herself.

Because sua agrees with menda, not directly with Lucia.

In Latin, adjectives must agree with the noun they describe in:

• gender
• number
• case

Here:

• menda = neuter plural accusative
• so the adjective must also be neuter plural accusative
• therefore: sua

Even though Lucia is feminine singular, sua is shaped to match menda.

Statim means immediately or at once.

It is an adverb modifying corrigit:

• statim corrigit = corrects immediately

Latin word order is flexible, so an adverb like statim can often move around without changing the basic meaning. Here it comes before the verb, which is very natural Latin.

Corrigit is:

• 3rd person singular
• present tense
• active voice
• indicative mood

from the verb corrigō, corrigere = to correct

So corrigit means:

• she corrects
• or he corrects, depending on the subject

Here the subject is Lucia, so:

• she corrects

Because the verb ending already tells you the person and number.

• corrigit = he/she/it corrects

Since Lucia is already the subject of the sentence, Latin does not need to repeat she. The subject is understood from the context.

Latin often leaves subject pronouns unstated unless they are needed for emphasis or clarity.

Latin word order is much freer than English word order because Latin uses endings to show grammatical function.

A very common neutral Latin order places the verb near or at the end of the clause:

• menda sua statim corrigit

That does not mean the sentence is unusually emphatic; it is simply a normal Latin arrangement.

English depends more on word order, but Latin depends more on endings.

Yes, in normal prose you would usually include est here.

• Lucia diligentior est = Lucia is more diligent

Latin does sometimes omit forms of sum (to be), especially in poetry, informal contexts, or where the meaning is very obvious. But for standard straightforward prose, est is the expected form.

This sentence is a good example of several basic Latin features:

1. Comparative adjective

   • diligentior = more diligent

2. Comparison with quam

   • quam Marcus = than Marcus

3. Reason clause

   • quia = because

4. Direct object

   • menda = mistakes

5. Reflexive possessive

   • sua = her own

6. Adverb

   • statim = immediately

7. Finite verb ending showing the subject

   • corrigit = she corrects

So even though the sentence is short, it contains several very common Latin patterns.