In foro multa pocula vilia sunt, sed haec pocula mater emere non vult.

Because in can take different cases depending on the meaning.

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

Here the cups already are in the forum, so Latin uses the ablative: in foro.

If someone were going into the forum, you would expect in forum.

Latin does not need a separate word like English there in this kind of sentence.

So multa pocula vilia sunt literally means many cheap cups are, and with in foro it becomes there are many cheap cups in the forum.

The verb sunt is just the normal verb are.

Because poculum is a neuter noun.

Neuter nouns of the second declension have these forms:

• singular nominative: poculum
• plural nominative: pocula
• plural accusative: pocula

So pocula means cups.
If it were a masculine second-declension noun, the plural might be -i, but neuter nouns use -a in the nominative and accusative plural.

Adjectives in Latin must agree with the noun they describe in:

• gender
• number
• case

Since pocula is neuter plural, its adjectives must also be neuter plural.

So:

• multa = many, agreeing with pocula
• vilia = cheap, also agreeing with pocula

A useful detail: multa comes from a first/second-declension adjective (multus, -a, -um), while vilia comes from a third-declension adjective (vilis, vile). Even though they belong to different adjective patterns, both are correctly agreeing with pocula.

It is nominative plural.

That is because pocula is the subject of sunt:

• multa pocula vilia sunt = many cheap cups are

In smoother English we say there are many cheap cups, but in Latin the cups themselves are the grammatical subject.

Because haec has to agree with pocula, which is neuter plural.

The demonstrative hic, haec, hoc means this or these. Its neuter plural form is haec.

So:

• haec pocula = these cups

The other forms would not match:

• hae is feminine plural
• hos is masculine accusative plural
• poculos would be masculine, but poculum is neuter

Good question, because with neuter plural nouns the nominative and accusative forms are often identical.

Here haec pocula could look either nominative or accusative just by form alone. But the sentence structure tells us its job:

• mater = the subject
• vult = wants
• emere = to buy
• what does she want to buy? haec pocula

So haec pocula is the direct object of emere, and therefore it is accusative plural, even though it looks the same as the nominative.

Because vult is followed by an infinitive in Latin, just like wants to buy in English.

• vult = she wants
• emere = to buy

So:

• mater emere non vult = mother does not want to buy

This is a very common Latin pattern:

• volo ambulare = I want to walk
• puer discere vult = the boy wants to learn

Because non negates the verb phrase: does not want.

So:

• vult = wants
• non vult = does not want

Latin word order is more flexible than English, so non is not always locked into one exact position, but placing it before the finite verb is very common and easy to understand.

Because Classical Latin has no articles.

English distinguishes:

• a cup
• the cup
• cups
• the cups

Latin does not do that with separate words. A noun like pocula can mean cups or the cups, depending on context.

So the sentence can naturally be understood as:

• there are many cheap cups in the forum, but mother does not want to buy these cups

The demonstrative haec makes the second pocula more definite: these cups.

Yes, but not in the same rigid way as in English.

Latin uses word order partly for grammar, but very often for emphasis and style, because the endings already show many grammatical relationships.

In this sentence:

• In foro comes first to set the scene: in the forum
• multa pocula vilia gives the important information about what is there
• sed haec pocula brings in a contrast: but these cups
• mater emere non vult finishes with the main point: mother does not want to buy

An English speaker should not assume Latin always follows normal English word order. The endings matter more than the position.