Pater contentus est, quia omnes domi adsunt.

Because contentus is agreeing with pater.

• pater is masculine singular nominative
• so the adjective describing him must also be masculine singular nominative
• that gives contentus

In this sentence, contentus est means is content or is satisfied. This is called a predicate adjective: the adjective describes the subject through the verb est.

If the subject were feminine, you would expect contenta est.

Yes, contentus means content / satisfied, but Latin still normally needs the verb to be in a sentence like this.

So:

• contentus = content
• est = is
• contentus est = is content

This works just like English Father is content. The adjective does not itself include the idea of is.

Latin has no articles. That means it does not have separate words for the or a/an.

So pater could mean:

• father
• a father
• the father

The context tells you which is most natural.

That is very normal in Latin, and learners coming from English often notice it quickly.

Quia introduces the reason: because.

So the sentence is structured like this:

• main clause: Pater contentus est
• reason clause: quia omnes domi adsunt

In other words, the second clause explains why the father is content.

Quia commonly takes the indicative, and that is what we see here with adsunt.

In Latin, omnes literally means all or all people, so it is plural.

That is why the verb is also plural:

• omnes = all / everyone
• adsunt = are present

English often uses singular everyone, but Latin here chooses a plural idea: all are present.

Also, omnes is the nominative plural form here, because it is the subject of adsunt.

Domi is a special form meaning at home.

It is a locative form of domus. The locative is an old case used mainly for place where, and it survives in a small number of words in Latin, especially:

• names of towns and small islands
• a few special words such as domi = at home

So:

• domi = at home
• not to home
• not from home

Compare:

• domum = homeward / to home
• domo = from home

Yes. Adsunt is from adsum, adesse, adfui, which is built from ad + sum.

It means to be present, to be here, or to be in attendance.

So:

• sunt = they are
• adsunt = they are present / they are here

In this sentence, adsunt is more precise than plain sunt, because the idea is not just that they exist, but that they are present at home.

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

So omnes domi adsunt literally has the order:

• all
• at home
• are present

That is perfectly natural in Latin.

The verb often comes near the end of the clause, and important words can be placed earlier for emphasis. Here omnes comes first in the second clause, which nicely highlights the reason for the father’s happiness: everyone is home.

Other orders could also be possible, such as domi omnes adsunt, but the given order is straightforward and idiomatic.

Originally, contentus is the perfect participle of contineo in a historical sense, but in ordinary Latin it is very commonly used simply as an adjective meaning content, satisfied, or well pleased.

So in a sentence like this, it is best understood as a normal adjective describing pater.

For a learner, the most useful point is this:

• treat contentus here as an adjective
• make it agree with the subject
• combine it with est to get is content

We know because pater is in the nominative singular, which is the normal case for the subject.

Also, contentus matches it in:

• case: nominative
• number: singular
• gender: masculine

And the verb est is singular, which also fits pater.

Meanwhile:

• omnes is the subject of the second clause
• adsunt is plural, agreeing with omnes

So the sentence has two clear subjects, one in each clause:

• pater in the main clause
• omnes in the quia clause