Nisi panis recens est, avia eum emere non vult.

Nisi means unless, or very literally if not. It introduces the condition for the main clause.

So:

Nisi panis recens est = Unless the bread is fresh / If the bread is not fresh

They can overlap, since both can mean if ... not. But nisi is the normal compact way to say unless.

So in this sentence, nisi is the most natural choice.
A learner can often think:

• nisi = unless
• si non = more literally if not

It is a conditional sentence:

• condition: Nisi panis recens est
• main clause: avia eum emere non vult

It is a simple present condition. Latin uses the present indicative here because the speaker is stating something as a real possibility or general rule, not as something imaginary or contrary to fact.

Because this is not a subjunctive or hypothetical condition. The sentence simply states a straightforward condition: if the bread is not fresh, grandmother does not want to buy it.

So Latin uses:

• est = present indicative, is

If the sentence were expressing a different kind of idea, such as a more hypothetical or stylistically different clause, Latin might use the subjunctive, but not here.

Because panis is the subject of est in the conditional clause.

In panis recens est, the structure is:

• panis = the bread
• recens = fresh
• est = is

So panis has to be nominative singular.

Also, panis is a third-declension masculine noun.

Recens is an adjective meaning fresh.

It agrees with panis in:

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

But Latin agreement does not mean the endings must look the same. Nouns and adjectives can belong to different declension patterns and still agree perfectly.

So panis recens is correct even though the endings are different.

It is related to English recent, but here fresh is the better meaning.

With food, recens commonly means:

• fresh
• newly made
• not stale

So in this sentence, fresh bread is the natural idea.

Because avia is the subject of vult.

In the main clause:

• avia = grandmother
• non vult = does not want

So avia must be nominative singular.

Because after vult (wants), Latin normally uses an infinitive to express what someone wants to do.

So:

• vult emere = wants to buy

This is a very common Latin pattern:

• volo + infinitive = want to ...

Also, emere is the present active infinitive of emo.

Avia is.

In a sentence like this, the subject of the infinitive emere is understood to be the same as the subject of the main verb vult, unless Latin says otherwise.

So:

• avia eum emere non vult = grandmother does not want to buy it

Grandmother is the one who would do the buying.

Eum is the accusative singular masculine form of the pronoun is, ea, id.

Here it refers back to panis. So it means it.

It is accusative because it is the direct object of emere:

• buy it

Because Latin follows grammatical gender, not just natural gender.

The noun panis is masculine, so the pronoun referring to it must also be masculine:

• panis → eum

English uses it for inanimate things, but Latin still chooses masculine, feminine, or neuter according to the noun’s grammatical gender.

It would be panem.

That is the accusative singular form of panis, and it would be needed because the bread is the direct object of emere.

So a version with the noun repeated would be:

avia panem emere non vult

Because the main idea being negated is wants:

• non vult = does not want

So avia eum emere non vult means grandmother does not want to buy it.

In Latin, word order is flexible, but putting non with the finite verb is very common and clear.

Not really. Latin word order is much freer than English word order.

This sentence puts the condition first:

• Nisi panis recens est, ...

Then the main clause follows:

• avia eum emere non vult

Also, eum emere stays together nicely as to buy it.

A different word order could still be grammatical, but this one is perfectly natural and easy to understand.