Magistra discipulae notam bonam dat, quia diligens est.

Because magistra is in the nominative case, which is the case normally used for the subject of a Latin sentence.

Here, magistra means the teacher, and she is the one doing the action of dat (gives), so she is the subject.

Here discipulae is in the dative singular, which is often used for the indirect object.

The verb dare means to give, and with give you usually have:

• someone who gives
• something that is given
• someone to whom it is given

So in this sentence:

• magistra = the teacher
• notam bonam = a good mark/grade
• discipulae = to the student

That is why discipula becomes discipulae here.

Because it is the direct object of dat. It is the thing being given, so it must be in the accusative case.

• nota becomes notam
• bona becomes bonam

The adjective bonam matches notam in:

• gender: feminine
• number: singular
• case: accusative

This agreement is a basic rule in Latin: adjectives agree with the nouns they describe.

In Latin, word order is much more flexible than in English because the endings show the grammar.

So both of these are possible:

• notam bonam
• bonam notam

Both mean the same thing: a good mark/grade.

That said, putting the adjective after the noun is very common in simple Latin sentences, especially in beginner texts.

Dat is:

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

It comes from the verb dare, meaning to give.

So dat means he/she/it gives.
In this sentence, it means she gives, because the subject is magistra.

Quia means because. It introduces a clause giving the reason for the main action.

So the structure is:

• main clause: Magistra discipulae notam bonam dat
• reason clause: quia diligens est

In other words, the sentence gives an action and then explains why it happens.

Because diligens is an adjective, not a verb.

Latin often uses esse (to be) with an adjective:

• diligens est = is diligent

So est links the subject to the description diligens.

English does the same thing:

• She is diligent

Without est, the clause would be incomplete.

Grammatically, it can be ambiguous when the subject is not repeated.

In a clause like quia diligens est, the subject is understood rather than stated explicitly. That understood subject could refer to:

• the teacher, or
• the student

In real context, the meaning usually makes it clear. Very often, in a sentence like this, the intended meaning is that the student is diligent, which explains why she receives a good mark. But strictly from the grammar alone, Latin does not force that interpretation unless the context makes it clear.

If a writer wanted to remove the ambiguity, they could make the subject more explicit.

Diligens is a third-declension adjective with one form for masculine and feminine in the nominative singular.

So:

• masculine singular: diligens
• feminine singular: diligens
• neuter singular: diligens

That is why it does not change to something like diligenta. The dictionary form is simply diligens, diligentis.

So even if it describes a female person such as magistra or discipula, diligens is still correct.

Often, yes. Because Latin uses case endings, the roles of the words are shown by their forms, not mainly by position.

For example, these would still basically mean the same thing:

• Magistra discipulae notam bonam dat
• Discipulae magistra notam bonam dat
• Notam bonam magistra discipulae dat

The endings still show:

• magistra = subject
• discipulae = indirect object
• notam bonam = direct object

However, changing the order can change the emphasis. Latin word order is often used to highlight certain words, even when the basic meaning stays the same.

Yes. In school-related contexts, nota commonly means a mark, grade, or school assessment.

Its basic meaning can also be something like sign, note, or mark, but in a sentence with teacher, student, and gives, the school meaning is the natural one.

So notam bonam dat is best understood as gives a good grade/mark.