Frater stultus sororem pauperiorem contemnit, sed mater ei irata est.

Because frater is in the nominative singular, which is the normal case for the subject of a clause.
Stultus is also nominative singular masculine, so it agrees with frater and means foolish.

So frater stultus means the foolish brother.

Latin word order is flexible, but putting the subject first is very common.

Because sororem pauperiorem is the direct object of contemnit.

• sororem is accusative singular of soror
• pauperiorem is also accusative singular feminine, agreeing with sororem

So they mean the poorer sister, and they are in the accusative because she is the person being despised.

Pauperiorem is the comparative form of pauper, meaning poorer.

It agrees with sororem in:

• gender: feminine
• number: singular
• case: accusative

So sororem pauperiorem means a poorer sister or the poorer sister, depending on context.

Latin often forms comparatives with a special comparative adjective ending, rather than using a separate word like English more.

So:

• pauper = poor
• pauperior = poorer

Then the ending changes to fit the noun it describes. Here, because it goes with sororem, it becomes pauperiorem.

Contemnit is a 3rd person singular present active indicative verb from contemnere.

That means:

• 3rd person singular: he/she despises
• present: happening now
• active: the subject does the action
• indicative: ordinary statement

So frater stultus sororem pauperiorem contemnit means the foolish brother despises the poorer sister.

Because the sentence has two clauses joined by sed:

1. Frater stultus sororem pauperiorem contemnit
2. sed mater ei irata est

Each clause has its own subject:

• first clause: frater
• second clause: mater

So mater is nominative because it is the subject of the second clause.

Ei is the dative singular form of the pronoun is, ea, id and here means to him, to her, or more naturally in English, with him/her after irata est.

The adjective iratus, irata, iratum often takes the dative in Latin:

• alicui iratus esse = to be angry with someone

So:

• mater ei irata est = the mother is angry with him/her

In context, ei most naturally refers to the brother.

Because irata is an adjective, not a complete verb by itself.

Latin often uses:

• adjective + sum

So:

• irata est = is angry

Here:

• irata is feminine nominative singular, agreeing with mater
• est supplies the verb is

So the phrase literally means mother is angry.

No. In this sentence, irata est is best understood as:

• irata = adjective, angry
• est = is

So it means is angry, not a completed action.

A beginner might confuse this with a perfect passive form, but here the meaning and syntax show that irata is simply a predicate adjective describing mater.

Latin often leaves out possessive words like his, her, or their when the relationship is obvious from context.

So sororem can simply mean sister, and in context English may translate it as his sister.

Latin does this much more freely than English.

Latin has no articles.

That means a noun like frater can mean:

• the brother
• a brother
• sometimes just brother

The exact sense comes from context. So:

• frater stultus could be the foolish brother or a foolish brother
• sororem pauperiorem could be the poorer sister or a poorer sister

English has to choose an article, but Latin does not.

In Latin, adjectives usually match their nouns in gender, number, and case.

Here:

• stultus matches frater
  
  • masculine, singular, nominative
• pauperiorem matches sororem
  
  • feminine, singular, accusative
• irata matches mater
  
  • feminine, singular, nominative

So even if the word order changed, the endings would still show the connections.

Yes, often it could.

For example, Latin could rearrange the words for emphasis, because the endings show the grammatical roles. The original order is quite natural, but something like Sororem pauperiorem frater stultus contemnit would still mean basically the same thing.

What changes most is the emphasis, not the core meaning.

By form alone, ei can mean:

• to him
• to her
• sometimes to it

So the form itself is not enough to tell us the gender.

Context decides. In this sentence, the most likely meaning is him, referring to frater, because the mother is angry with the foolish brother for despising his sister. But grammatically, ei itself is not exclusively masculine.