Post meridiem puellae ad colligendas uvas iterum venire volunt, sed mater dicit uvas nondum maturas esse.

Because puellae can be several different case forms, but the verb tells you which one it is here.

The verb volunt means they want, so it needs a plural subject. That makes puellae nominative plural: the girls.

So:

• puellae ... volunt = the girls want ...

Even though puellae can also mean of the girl, to the girl, or for the girl in other contexts, those meanings do not fit with volunt here.

Post meridiem means after midday, often naturally translated as in the afternoon.

The preposition post takes the accusative case, so meridiem is accusative singular.

Breaking it down:

• post = after
• meridies = midday, noon
• post meridiem = after noon

This is also the source of the English abbreviation p.m.

Latin often expresses purpose with ad plus a verbal noun or verbal adjective construction. Here, ad colligendas uvas means for gathering grapes or more naturally to gather grapes.

This is a very common Latin way to show purpose:

• ad
  • accusative = for the purpose of ...

So:

• ad colligendas uvas = to gather grapes

English uses the infinitive very freely, but Latin often prefers a purpose phrase like this.

Colligendas is a gerundive, sometimes also called the future passive participle in school grammar.

It comes from colligere, meaning to collect or to gather.

Here it is:

• feminine
• accusative
• plural

It matches uvas, because the grapes are the thing being gathered.

So:

• uvas = accusative plural feminine
• colligendas = accusative plural feminine

Together:

• ad colligendas uvas = literally for grapes to be gathered
• more naturally: to gather grapes

Because in this kind of construction, the gerundive acts like an adjective and agrees with the noun it describes.

So just as an ordinary adjective would agree with uvas, the gerundive does too:

• uvas maturas = ripe grapes
• uvas colligendas = grapes to be gathered

That is why both words are accusative plural feminine.

Iterum means again, and it is an adverb. Latin word order is much freer than English word order, so adverbs can often appear in different places without changing the basic meaning.

Here:

• puellae ad colligendas uvas iterum venire volunt

means:

• the girls want to come again to gather grapes

You could also see slightly different word orders in Latin with the same general sense. The placement of iterum here emphasizes that the coming is being repeated.

Both are possible in Latin.

Latin infinitives can come before or after the main verb, especially with verbs like volo (want). So:

• venire volunt
• volunt venire

both mean they want to come.

The choice is mostly about style, rhythm, and emphasis rather than a big grammatical difference.

Because Latin commonly uses indirect statement after verbs of saying, thinking, knowing, and perceiving.

In English we say:

• Mother says that the grapes are not yet ripe

Latin instead usually says:

• mater dicit uvas nondum maturas esse

This pattern is called the accusative and infinitive construction:

• uvas = accusative subject of the indirect statement
• esse = infinitive
• maturas = predicate adjective agreeing with uvas

So literally it is:

• mother says the grapes to be not yet ripe

but in normal English:

• mother says that the grapes are not yet ripe

Because in a Latin indirect statement, the subject does not stay in the nominative. It becomes accusative.

So in a direct statement you would have:

• uvae nondum maturae sunt = the grapes are not yet ripe

But after dicit, Latin changes this into indirect statement:

• dicit uvas nondum maturas esse

So:

• uvae becomes uvas
• maturae becomes maturas
• sunt becomes esse

That is a standard Latin pattern.

Because maturas is describing uvas.

Even though maturas is part of an indirect statement, it still agrees with the noun it describes:

• uvas = accusative plural feminine
• maturas = accusative plural feminine

So uvas maturas esse means the grapes to be ripe, or in better English, that the grapes are ripe.

Nondum means not yet.

That is stronger and more specific than just non, which simply means not.

So:

• uvas non maturas esse would mean that the grapes are not ripe
• uvas nondum maturas esse means that the grapes are not ripe yet

The word nondum suggests that they may become ripe later, but the time is not right now.

Because the two instances of uvas have different grammatical jobs.

First:

• ad colligendas uvas
• here uvas is the object of the gathering: to gather grapes

Second:

• mater dicit uvas nondum maturas esse
• here uvas is the accusative subject of the indirect statement: that the grapes are not yet ripe

So the same word appears twice, but it is doing two different things in the sentence.