Bona lectio discipulis non solum vocabula nova, sed etiam artem disputandi docet.

Because bona lectio is in the nominative singular, which is the normal case for the subject. The verb docet is also third person singular, so it matches a singular subject.

This is a good example of an important Latin habit: case endings matter more than word order. Even though English usually depends on position, Latin usually tells you the job of a word by its ending.

Because bona has to agree with lectio.

Lectio is:

• feminine
• singular
• nominative

So the adjective must also be:

• feminine
• singular
• nominative

That gives bona. Latin adjectives agree with the nouns they describe in gender, number, and case.

Discipulis is dative plural, meaning to the students or for the students.

A learner may notice that docere is often taught with two accusatives in classical Latin: aliquem aliquid docere = to teach someone something. So a very classical version might use discipulos instead.

But Latin can also use the dative for the person taught, and that is what this sentence does. So here discipulis functions like an indirect object: the good lesson teaches things to the students.

Both are accusative, because they are the things being taught.

So:

• vocabula nova = new words / new vocabulary items
• artem disputandi = the art of disputing / debating

They are the direct objects of docet. The sentence says that a good lesson teaches these things to the students.

Because vocabulum is a neuter second-declension noun.

For neuter nouns of this type:

• singular nominative/accusative: -um
• plural nominative/accusative: -a

So:

• vocabulum = one word / vocabulary item
• vocabula = words / vocabulary items

This is very common in Latin. A neuter plural ending in -a is something you will see constantly.

Because nova agrees with vocabula.

Since vocabula is:

• neuter
• plural
• accusative

the adjective must match it:

• neuter
• plural
• accusative

That produces nova. So vocabula nova means new words or new vocabulary.

Disputandi is a gerund in the genitive singular.

A gerund is a verbal noun. Here it means something like of disputing, of debating, or of argumentation.

So:

• ars = art, skill
• artem = the accusative form of ars
• artem disputandi = the art of disputing

Latin often uses a genitive gerund after a noun like ars to express the art of doing something.

This is a standard Latin pair meaning not only ... but also.

So the structure is:

• non solum vocabula nova
• sed etiam artem disputandi

In other words, the good lesson teaches not only new words, but also the art of disputing.

It is a fixed correlative pattern, and it is very common in Latin prose.

Because Latin word order is much more flexible than English word order. An adjective can often come before or after its noun.

So both of these are possible in Latin:

• nova vocabula
• vocabula nova

The endings show that the words belong together, so Latin does not need a rigid adjective position the way English usually does.

Docet is:

• present tense
• active voice
• indicative mood
• third person singular

It comes from docere, meaning to teach.

So docet means he/she/it teaches. Here, since the subject is bona lectio, the meaning is a good lesson teaches.

Because Latin has no articles. It does not have separate words that exactly match English a, an, or the.

So bona lectio can mean:

• a good lesson
• the good lesson

The exact choice in English depends on context. Latin leaves that unstated unless something else makes it definite or indefinite.

Because artem is the accusative singular form of ars.

The dictionary form is ars because that is the nominative singular. But in this sentence the word is a direct object of docet, so it must be in the accusative:

• nominative: ars
• accusative: artem

This is a normal third-declension change.