In triclinio pater matri gratias agit, quod convivas benigne accepit.

Because in takes the ablative when it means in or on in the sense of location.

• in triclinio = in the dining room
• in triclinium would mean into the dining room, with motion toward a place

So the case tells you whether the phrase is about where something is happening or where something is going.

Pater is in the nominative singular, which is the normal case for the subject of a sentence.

Its basic form is:

• pater = father

Since Latin uses case endings rather than strict word order to show sentence function, pater is recognized as the subject because of its form, not just because of its position.

Latin normally has no articles. So pater can mean:

• the father
• a father

and convivas can mean:

• the guests
• guests

You decide from context which English wording is best.

Because gratias agere takes a person in the dative.

• alicui gratias agere = to give thanks to someone / to thank someone

So:

• matri = to the mother / mother as the person being thanked

This is a standard idiom in Latin.

Latin often uses the idiom gratias agere, literally to give thanks, for the idea to thank.

So:

• gratias agit = he gives thanks = he thanks

This is just the normal Latin expression. English uses one main verb, but Latin commonly uses this noun-plus-verb idiom.

Because the idiom is normally gratias agere, with gratias in the plural accusative.

That plural is idiomatic. You should think of it as a fixed expression rather than try to force a literal English equivalent for the number.

Also, gratia in the singular often has meanings like favor, grace, or influence, while gratias agere is the standard phrase for thanking someone.

Because conviva is a first-declension noun, and first-declension nouns usually have forms like -a, -ae, -am, -as. Although many first-declension nouns are feminine, some are masculine, especially words for male persons or social roles.

So:

• conviva = guest
• convivas = guests, as the accusative plural

Its ending shows declension pattern, not automatic biological gender.

Because convivas is the direct object of accepit.

The verb accipere here means to receive or welcome, so the people being received are in the accusative:

• convivas benigne accepit = welcomed the guests kindly

Benigne is an adverb, meaning kindly, graciously, or in a friendly way. It modifies the verb accepit.

So it tells you how the guests were received:

• accepit = received
• benigne accepit = received kindly

Here quod means because and introduces a causal clause.

So the structure is:

• main clause: pater matri gratias agit
• reason clause: quod convivas benigne accepit

In other words, the father thanks the mother because the guests were welcomed kindly.

This is different from quod used as a relative pronoun meaning which or the fact that, although the forms are the same.

Because this quod clause gives a reason presented as a fact from the speaker’s point of view.

So Latin uses the indicative:

• accepit = she/he received

If the sentence were presenting the reason as someone’s idea, allegation, or more subjective explanation, Latin might use different constructions. But here the reason is treated straightforwardly as real.

The sentence expects you to understand the subject from context. The form accepit only means he/she/it received; it does not show gender.

Given the sense of the sentence, the understood subject is the mother: the father thanks the mother because she welcomed the guests kindly.

This is a good reminder that Latin often leaves subjects unstated when they can be inferred. If a writer wanted to make it more explicit, Latin could add a noun or pronoun.

Because the two verbs describe actions at different times.

• agit is present: the father is thanking now
• accepit is perfect: the mother welcomed the guests earlier, as a completed action

So the sentence means that the present act of thanking is happening because of an earlier completed action.

Not in the same way it is in English. Latin word order is relatively flexible because the endings show the grammar.

This order:

• In triclinio pater matri gratias agit, quod convivas benigne accepit

puts the setting first, then the main action, then the reason.

A different order could still mean the same thing, though it might change the emphasis. For example, starting with matri would emphasize the person being thanked more strongly.