Non est discipulus qui hoc exercitium sine cura perficiat; omnibus enim tempus et patientia necessaria sunt.

Because qui hoc exercitium sine cura perficiat is a relative clause of characteristic.

Latin often uses a relative clause with the subjunctive to describe the kind of person who would fit a description, rather than a specific person already known to exist. So:

• Non est discipulus qui ... perficiat = There is no student who would/could complete ...
• It means something like No student is the sort of person to complete this exercise without care.

If Latin used the indicative here, it would sound more like a simple factual description of a specific existing student or students, not this more general idea.

The negative antecedent non est discipulus also makes this kind of subjunctive especially common.

Latin often uses the singular in this kind of statement to express a general truth:

• non est discipulus qui ... = there is no student who ...

This is idiomatic and very common. English can do something similar:

• There is no student who can do this
• rather than There are no students who can do this

Both ideas are possible, but the singular in Latin often gives a neat, generalizing sense.

Here qui means who and refers back to discipulus.

So the structure is:

• discipulus = student
• qui ... perficiat = who would/could complete ...

Because discipulus is masculine singular nominative, the relative pronoun is also qui:

• masculine singular nominative = qui

It is the subject of perficiat.

Because it is the direct object of perficiat.

• perficere means to complete / finish
• What is being completed? hoc exercitium = this exercise

So:

• hoc = accusative singular neuter of hic, haec, hoc
• exercitium = accusative singular neuter

Together: hoc exercitium = this exercise

Because the preposition sine takes the ablative.

• sine = without
• cura = ablative singular of cura

So:

• sine cura = without care

This is just a normal prepositional phrase. A learner should remember:

• sine + ablative

It means not simply without care in the emotional sense, but more like:

• without careful attention
• carelessly
• without taking proper pains

So the sentence is saying that nobody can finish this exercise properly if they approach it carelessly or without due attention.

Because enim is a postpositive word in Latin.

That means it usually comes after the first word or phrase of its clause, even though in English we translate it as for, indeed, or because.

So:

• omnibus enim = for to everyone / for everyone

Not:

• enim omnibus

This is very normal Latin word order.

Because omnibus means for everyone or to everyone, and it is used with necessaria sunt.

So the idea is:

• tempus et patientia necessaria sunt omnibus
• time and patience are necessary for everyone

This is a common Latin construction:

• alicui necessarius, -a, -um esse = to be necessary for someone

Thus:

• omnibus = dative plural, for all / for everyone

Because they are the subjects of sunt.

The second clause literally says:

• time and patience are necessary for everyone

So:

• tempus = nominative singular neuter
• patientia = nominative singular feminine
• sunt = plural, because there are two subjects joined by et

Even though each noun is singular by itself, together they form a plural subject.

Because it agrees with the compound subject tempus et patientia.

Since there are two things being described, the predicate adjective is plural:

• tempus et patientia necessaria sunt
• time and patience are necessary

There is also an additional detail: the two nouns have different genders:

• tempus = neuter
• patientia = feminine

When Latin has a predicate adjective with nouns of different genders, it often uses the neuter plural. That is what necessaria is here.

So necessaria is plural because there are two subject nouns, and neuter because the genders are mixed.

Because here tempus means time in a general, uncountable sense, not times as separate occasions.

English does the same thing:

• Time and patience are necessary
• not usually times and patience are necessary

So the singular is exactly what we would expect.

It has two main parts joined by a semicolon:

1. Non est discipulus qui hoc exercitium sine cura perficiat

   • There is no student who would/could complete this exercise without care

2. omnibus enim tempus et patientia necessaria sunt

   • for everyone, time and patience are necessary

The second clause explains the first:

• No one can do it carelessly,
• because everyone needs time and patience.

So enim introduces the reason or explanation.

Yes. In this sentence, English may use several natural translations depending on the tone:

• There is no student who would complete this exercise without care
• There is no student who can complete this exercise without care
• No student could complete this exercise without care

The Latin subjunctive here does not map neatly onto one single English form. The main idea is that such a student does not exist; no one is the kind of person able to do this successfully without care.

Because Latin uses endings to show grammatical relationships, so word order is much freer than in English.

For example:

• hoc exercitium is clearly the object because it is accusative
• omnibus is clearly dative
• tempus et patientia are clearly subjects
• necessaria matches them as a predicate adjective

That allows Latin to arrange words for emphasis and style. Here, the order helps the sentence sound balanced and rhetorical:

• first the claim: no student...
• then the explanation: for everyone...

Yes, several very useful patterns appear here:

• non est + noun + qui + subjunctive
  a common way to say there is no one who would/could...

• sine + ablative
  without ...

• enim in second position
  for / indeed / you see

• dative + necessarius esse
  to be necessary for someone

• compound subject + plural verb
  tempus et patientia ... sunt

So this sentence is a good example of how Latin combines ordinary case usage with a more advanced subjunctive construction.