Conviva matri gratias agit, quod epulae simplices sed bonae sunt.

Because matri is the dative singular form of mater, and the verb phrase gratias agere takes the person thanked in the dative.

So:

• mater = mother as a subject
• matri = to the mother / to mother

In this sentence, the guest is thanking the mother, so Latin uses matri.

Gratias agit is a very common Latin idiom meaning gives thanks or simply thanks.

Literally:

• gratias = thanks (accusative plural)
• agit = does / drives / acts

Together, gratias agere means to give thanks.

Latin often uses an idiomatic expression where English might use a single verb. So instead of one standalone verb meaning to thank, classical Latin very often says gratias agere.

Because Latin normally says gratias agere, not gratiam agere, when meaning to give thanks.

So gratias here is part of a fixed expression. English does something similar: we usually say thanks, which is also plural in form, even when we mean a single act of gratitude.

Because not all first-declension nouns are feminine.

Conviva is a first-declension noun, but it can refer to a male or female guest depending on context. A learner often expects -a nouns to be feminine, but Latin has some important exceptions.

So here:

• conviva = guest (subject of the sentence)
• the ending -a tells you its declension, not automatically its gender

Epulae is very often a plural noun in Latin. It can mean feast, banquet, or dishes/food served at a meal, and it is commonly used in the plural even when English might use a singular word.

So the sentence uses:

• epulae = the meal / the dishes / the feast

This is one of those nouns whose Latin grammar does not match English exactly.

Because they agree with epulae.

In Latin, adjectives must agree with the noun they describe in:

• gender
• number
• case

Since epulae is feminine plural nominative, the adjectives describing it must also be feminine plural nominative:

• simplices
• bonae

So both adjectives match epulae grammatically.

Because simplex and bona would be singular forms, but epulae is plural.

Here is the agreement:

• epulae = feminine plural nominative
• simplices = feminine plural nominative
• bonae = feminine plural nominative

So Latin is saying that the dishes are simple and good, both in the plural.

Here quod is a conjunction meaning because.

It introduces the reason why the guest thanks the mother:

• Conviva matri gratias agit = the guest thanks the mother
• quod epulae simplices sed bonae sunt = because the dishes are simple but good

So quod connects the main statement to the reason for it.

Because this is a straightforward factual reason clause.

Latin often uses quod + the indicative when the speaker presents the reason as a fact:

• quod epulae simplices sed bonae sunt
• because the dishes are simple but good

If Latin wanted a different nuance, especially in some authors or in reported reasoning, another construction might appear. But here the indicative is the normal, simple choice.

Because its subject is epulae, which is plural.

• epulae = plural subject
• sunt = are, plural form of esse

So Latin matches the verb to the number of the subject, just as English does.

Latin word order is much more flexible than English word order because the endings show each word’s role in the sentence.

Here:

• conviva is the subject
• matri is the indirect object
• gratias is part of the idiom gratias agere
• agit is the verb

A Roman could rearrange these words more easily than an English speaker can, though some orders are more natural than others. The given order is perfectly normal and puts the verb at the end of the main clause, which is very common in Latin.

Yes, it could have been omitted, but the meaning would change slightly in tone.

With sed, the sentence emphasizes a contrast:

• the dishes are simple, but good

Without sed, it would sound more like a simple list of qualities:

• the dishes are simple and good

So sed adds the idea that simplicity might seem unimpressive at first, yet the food is still good.

In modern printed Latin, commas are often added to help readers, especially before subordinate clauses like the one introduced by quod.

In ancient manuscripts, punctuation was much less standardized. So the comma is helpful for us, but it is not something you should treat as a core grammatical feature of the sentence.

Yes, quod can also be a relative pronoun meaning which, depending on context. But here it is clearly a conjunction meaning because.

You can tell because:

• it introduces a full clause
• that clause gives the reason for the main action
• there is no obvious neuter singular antecedent for quod to refer back to

So in this sentence, quod is best understood as because, not which.

Because the two adjectives belong to different declension patterns.

• simplex, simplicis is a third-declension adjective
• bonus, bona, bonum is a first/second-declension adjective

Even though both agree with epulae in gender, number, and case, they show that agreement using the endings of their own declension type:

• simplices = feminine plural nominative, third-declension pattern
• bonae = feminine plural nominative, first/second-declension pattern

So they match the same noun, but they do not have to look identical.