Discipulus magistro veritatem dicit, quia mendacio non credit.

With dīcere (to say/tell), Latin commonly uses:

• accusative for the thing said
• dative for the person told

So magistro is dative singular (“to the teacher”), while veritatem is the thing being told.

Grammatically it can be taken either way, but Latin structure here strongly matches English tell + person + thing:

• The student tells the teacher the truth.

English “say the truth to the teacher” is possible but less natural; Latin dicit comfortably covers both “says” and “tells” depending on the objects.

Mendaciō is dative singular of mendācium (2nd declension neuter). It’s dative because crēdere (to believe) typically takes a dative object in Latin: you “believe to someone/something.”

So:

• mendaciō nōn crēdit = “he/she does not believe a lie” (literally “does not believe to a lie”).

Quia means because and normally introduces a reason clause with the indicative when the speaker presents the reason as a fact. So credit is present indicative: “because he/she does not believe…”

(If Latin wanted to present the reason as someone’s claimed reason or a more “reported”/subjective reason, it might use the subjunctive in some contexts, but quia + indicative is the basic pattern.)

Both are present indicative active, 3rd person singular:

• dicit = “he/she says / tells”
• credit = “he/she believes”

Latin often leaves out explicit subject pronouns (he/she) because the verb ending already encodes person and number.

The meaning is mostly carried by case endings, so you can rearrange it without changing the core grammar, e.g.:

• Veritatem discipulus magistro dicit...
• Discipulus veritatem dicit magistro...

That said, the given order is very natural: subject → indirect object → direct object → verb, then the quia clause.

Nōn usually comes directly before the word (or phrase) it negates; with a simple verb, it typically comes right before the verb:

• nōn crēdit = “does not believe”

You can find other placements in poetry or for emphasis, but non + verb is the standard prose pattern.

Yes, it would be broadly the same in meaning. Changing the order mainly changes emphasis and flow:

• Starting with mendacio non credit foregrounds the refusal to believe the lie.
• Starting with discipulus magistro veritatem dicit foregrounds the truth-telling to the teacher.

The grammar remains clear because magistro and mendacio stay dative and veritatem stays accusative.