Discipuli dicunt nihil facilius esse quam menda corrigere, si exemplum optimum ante oculos habent.

Because after a verb of saying like dicunt, Latin normally uses indirect statement: an accusative + infinitive construction.

So the direct statement would be:

Nihil facilius est quam menda corrigere.
= Nothing is easier than correcting mistakes.

But when reported after dicunt, it becomes:

Discipuli dicunt nihil facilius esse quam menda corrigere.

So esse is not random; it is the normal infinitive used in reported speech.

The subject of esse is nihil.

In an indirect statement, the subject is normally put in the accusative. With nihil, the form looks the same, so you do not see a visible change here. But functionally, nihil is the subject of esse inside the reported statement.

So the structure is essentially:

discipuli dicunt + [nihil facilius esse quam menda corrigere]

Facilius is the neuter singular comparative of facilis.

It agrees with nihil, which is neuter singular in sense. Latin often uses a neuter comparative after words like nihil:

• nihil melius = nothing better
• nihil facilius = nothing easier

So facilius is the correct form because it matches nihil.

This is a standard comparative pattern:

• nihil facilius = nothing easier
• quam = than

So:

nihil facilius esse quam menda corrigere
literally = that nothing is easier than to correct mistakes

In smoother English, we usually say:

that nothing is easier than correcting mistakes

Here corrigere is used after quam to express the action being compared: than correcting mistakes.

Latin often uses the infinitive where English might prefer a gerund:

• Latin: quam menda corrigere
• English: than correcting mistakes

A very literal English version would be than to correct mistakes, but normal English usually prefers than correcting mistakes in this sentence.

Because mendum is a neuter noun of the second declension, and neuter plural nominative and accusative endings are -a.

So:

• singular: mendum
• plural: menda

Here menda is accusative plural, the direct object of corrigere:

corrigere menda = to correct mistakes

This often surprises English speakers because menda may look like a first-declension singular form, but it is actually neuter plural.

Because this is a simple, real condition:

si exemplum optimum ante oculos habent
= if they have an excellent/the best example before their eyes

Latin normally uses the indicative in straightforward conditions like this. There is no special uncertainty or unreality being expressed.

So the sense is:

They say this is true if they have a good model in front of them.

It is both literal and idiomatic.

Literally:

• ante = before, in front of
• oculos = eyes
• habent = they have

So: they have it before their eyes

Idiomatic Latin uses ante oculos habere to mean:

• to have something clearly in view
• to keep something before one as a model
• to see something plainly

In this sentence, it suggests having a model copy or example right there to look at while correcting mistakes.

Optimum agrees with exemplum.

• exemplum is neuter singular
• optimum is the neuter singular form of optimus

So exemplum optimum means the best example, an excellent example, or an ideal model, depending on context.

In this sentence, exemplum probably means not just any example, but a model to follow.

Because Latin has no articles.

So Latin does not have separate words for a, an, or the. The context tells you which English article to use.

For example:

• discipuli can mean students or the students
• exemplum optimum can mean the best example or an excellent example

English has to choose an article when translating; Latin does not.

Latin word order is much more flexible than English word order, because the endings show the grammatical relationships.

This sentence puts the main reported idea first:

Discipuli dicunt nihil facilius esse quam menda corrigere

and then adds the condition:

si exemplum optimum ante oculos habent

That is a natural way to organize the thought: first the claim, then the condition under which it is true.

Other orders would be possible in Latin, but this one is clear and idiomatic.