Animus matris aeger est, quia filius abest.

Matris is the genitive singular of mater, so it means of the mother or the mother's.

So animus matris means the mother's mind/spirit/heart.

If Latin used mater here, that would make mother nominative, which would suggest that mother is the subject. But in this sentence, the subject is animus.

The subject of the main clause is animus.

You can tell because:

• animus is in the nominative singular
• est is third-person singular
• aeger is also nominative singular masculine, agreeing with animus

So the structure is basically:

• Animus = subject
• aeger est = is sick/distressed

Because aeger agrees with animus, and animus is a masculine noun.

In Latin, adjectives agree with the nouns they describe in:

• gender
• number
• case

So:

• animus = masculine singular nominative
• aeger = masculine singular nominative

Even though matris refers to a woman, aeger does not describe matris. It describes animus.

Animus can mean mind, spirit, heart, feeling, or inner state, depending on context.

Here it does not mean a physical organ. It refers to the mother's emotional or mental state. So the sentence is expressing something like:

• the mother's heart is troubled
• the mother's spirit is distressed
• the mother's mind is unwell

It is a more Latin way of expressing an emotional condition than simply saying the mother is sad.

It can mean both.

Aeger often means sick, ill, or unwell, but it can also be used metaphorically for emotional distress or mental trouble.

In this sentence, because the reason is quia filius abest (because her son is away/absent), it is most naturally understood emotionally: the mother is troubled, heartsick, or distressed.

Latin often expresses feelings in a more concrete or literary way by talking about the mind, spirit, or heart.

• Mater aegra est would mean the mother is sick/unwell
• Animus matris aeger est focuses specifically on her inner emotional state

So this version is more like saying:

• the mother's heart is troubled
• the mother's spirit is distressed

It is not exactly the same nuance as simply saying the mother is sick.

Quia means because.

It introduces a clause that gives the reason for the main statement.

So the sentence divides like this:

• Animus matris aeger est = the mother's spirit is distressed
• quia filius abest = because her son is away

Filius is the subject of the clause introduced by quia.

It is nominative singular, and it goes with abest:

• filius abest = the son is absent / the son is away

So the sentence has two clauses, each with its own subject:

• main clause: animus
• subordinate clause: filius

Because abest is the regular form of the verb absum, which means to be away, to be absent.

It is a compound of:

• ab- = away
• sum / est = am / is

So:

• abest = he/she/it is away or is absent

This is not written as two separate words in normal Latin.

It is common, but it is a little unusual because it is a compound of sum.

Since sum is irregular, compounds built from it are also learned as special forms. Some useful forms are:

• absum = I am away
• abes = you are away
• abest = he/she/it is away
• absunt = they are away

So abest is best learned as part of the verb absum.

The word order is natural Latin, but Latin word order is more flexible than English word order.

This sentence puts the main statement first and the reason second:

• Animus matris aeger est, quia filius abest.

Latin could also say:

• Quia filius abest, animus matris aeger est.

That would still mean the same thing, though the emphasis would shift slightly by putting the reason first.

Yes, literally that is very good.

But in smoother English, depending on context, you might choose:

• the mother's mind
• the mother's heart
• the mother's spirit

The best choice depends on how emotional or literal you want the English to sound.

It is a linking verb + predicate adjective construction.

• est = is
• aeger = adjective describing the subject

So this works like:

• puer laetus est = the boy is happy
• puella parva est = the girl is small
• animus matris aeger est = the mother's spirit is distressed

The adjective is in the nominative because it describes the subject through est.