Pauper, quae nihil in crumena habet, panem emere non potest.

Because pauper is a third-declension adjective, and in the nominative singular it has the same form for masculine and feminine.

So:

• pauper vir = a poor man
• pauper femina = a poor woman

In your sentence, we know pauper is feminine because of quae, which is the feminine singular relative pronoun.

Also, pauper here is being used like a noun: the poor woman or a poor woman.

Quae is the nominative feminine singular form of the relative pronoun qui, quae, quod.

It refers back to pauper, so it means who here:

• pauper, quae... = the poor woman, who...

It is feminine singular because its antecedent, pauper, is feminine singular in this sentence.

A key rule is:

• a relative pronoun agrees with its antecedent in gender and number
• but its case depends on its job inside the relative clause

Here, quae is the subject of habet, so it is nominative.

Because Latin qui, quae, quod can mean who, which, or that, depending on the context.

Since quae refers to a person, English naturally uses who:

• pauper, quae nihil in crumena habet = the poor woman, who has nothing in her purse

If it referred to a thing, English might use which or that instead.

The comma marks off the relative clause:

• quae nihil in crumena habet = who has nothing in her purse

This is similar to English writing, where a non-essential clause is often set off by commas.

So the sentence is structured like this:

• Pauper = main noun/subject
• quae nihil in crumena habet = extra information about that subject
• panem emere non potest = main statement

Nihil means nothing, and here it is the direct object of habet.

So:

• nihil habet = she has nothing

Traditionally, nihil comes from nihilum, but in normal Latin it is treated as an indeclinable word in many contexts. For a learner, the important thing is simply:

• nihil = nothing
• after habet, it functions as the object

Because in can take two different cases, depending on meaning:

• in + ablative = in / on a place, showing location
• in + accusative = into / onto a place, showing motion toward

Here the meaning is in the purse, not into the purse, so Latin uses the ablative:

• in crumena = in the purse

If the idea were motion into the purse, you would expect in crumenam.

Because it follows in in the sense of location.

The noun is crumena, crumenae (feminine, first declension). Its ablative singular is crumena.

So:

• nominative: crumena
• ablative singular: crumena

Even though the form looks the same as the nominative, its role is ablative because of the preposition in with the meaning in.

Because panem is the direct object of emere.

The noun is:

• panis = bread

Its accusative singular is:

• panem

So:

• panem emere = to buy bread

This is very common in Latin: the thing being bought, seen, heard, loved, etc. goes into the accusative.

Because possum (I am able / can) is commonly followed by an infinitive.

So:

• potest emere = she can buy
• literally, she is able to buy

This is called a complementary infinitive, because the infinitive completes the meaning of potest.

In your sentence:

• panem emere non potest = she cannot buy bread

Latin word order is much more flexible than English word order because the endings show the grammatical roles.

English depends heavily on position:

• The woman buys bread

Latin can move words around more freely because:

• panem is clearly accusative
• potest is the finite verb
• emere is the infinitive

So panem emere non potest is perfectly natural Latin.

A more English-like order might still be understandable, but Latin often places emphasis differently. Here the important idea builds toward the end:

• cannot buy bread

Because non normally negates the word or phrase that follows, and here it negates the verbal idea:

• non potest = is not able / cannot

Since potest and emere go together, non potest effectively negates the whole idea can buy.

So:

• panem emere non potest = she cannot buy bread

Yes. Pauper is the main subject of the sentence.

The relative clause has its own subject:

• quae ... habet = who ... has

So there are two linked parts:

1. Pauper ... non potest

   • The poor woman ... cannot

2. quae nihil in crumena habet

   • who has nothing in her purse

This is why both pauper and quae are nominative: one is the subject of the main clause, and the other is the subject of the relative clause.

Because Latin has no articles.

So a noun like pauper can mean:

• a poor woman
• the poor woman

and panem can mean:

• bread
• a loaf of bread
• the bread

You decide from the context which English article sounds best.

Yes in form, but here it is being used substantively, which means an adjective is used as if it were a noun.

So although pauper is basically an adjective meaning poor, in this sentence it means:

• a poor person
• more specifically here, a poor woman

Latin does this very often. English does something similar in phrases like the rich or the poor, though Latin can do it even more freely.