Avia dicit nuces bonas esse, sed infanti tantum pirum dari oportere.

Latin usually does not use a separate word for that after a verb of saying or thinking. Instead, it often uses an indirect statement construction.

Here:

• Avia dicit nuces bonas esse
• literally: Grandmother says nuts to be good
• natural English: Grandmother says that nuts are good

So nuces bonas esse is Latin’s way of expressing that nuts are good.

The same idea continues after sed:

• [avia dicit] infanti tantum pirum dari oportere
• [grandmother says] that only a pear ought to be given to the child

Because after dicit, Latin expects an indirect statement, and the subject of the infinitive is normally put in the accusative.

So in nuces bonas esse:

• nuces = accusative plural, subject of esse
• bonas agrees with nuces
• esse = infinitive

A very helpful clue is bonas. That form is clearly accusative feminine plural, so it shows that nuces is being treated as accusative too.

If this were a direct statement, it would be:

• nuces bonae sunt = the nuts are good

But after dicit, it becomes:

• nuces bonas esse = that the nuts are good

Because nux, nucis is a feminine noun in Latin.

So:

• nuces = nuts
• bonas = good

The adjective has to agree with the noun in:

• gender
• number
• case

Since nuces is feminine plural accusative here, bonas must also be feminine plural accusative.

Because this is indirect statement.

In a direct statement, Latin would say:

• nuces bonae sunt = the nuts are good

But after a verb like dicit, the finite verb sunt usually changes into the infinitive esse:

• dicit nuces bonas esse = she says that the nuts are good

So esse is not random; it is the normal form used in reported speech.

Yes. The verb dicit is understood with both parts.

You can think of the sentence as:

• Avia dicit nuces bonas esse
• sed [avia dicit] infanti tantum pirum dari oportere

So sed is connecting two things that the grandmother says:

1. nuces bonas esse
2. infanti tantum pirum dari oportere

Latin often leaves out a repeated verb when it is easy to understand.

Dari is the present passive infinitive of do, dare, meaning to be given.

So:

• dare = to give
• dari = to be given

It is passive because the sentence is focused on the thing being given, not on the person doing the giving.

So the idea is not someone should give only a pear to the child, but rather:

• only a pear ought to be given to the child

That is a very natural use of the passive in Latin.

Because infanti is the person to whom something is given.

With do, dare and its passive dari, the recipient is normally in the dative:

• infanti = to the child

So in:

• infanti tantum pirum dari

the meaning is:

• for only a pear to be given to the child
• more naturally, for only a pear to be given to the child

The key point is that infanti is the recipient, so Latin uses the dative.

Because oportet / oportere commonly uses an accusative + infinitive type of construction.

Compare:

• me ire oportet = I ought to go
• literally, it is proper for me to go

Here:

• pirum dari oportere

means:

• that a pear ought to be given

So pirum is the accusative subject of the infinitive dari after oportere.

It is not the direct object of dicit.

Because the two infinitives are doing different jobs.

• dari depends on oportere
• oportere depends on dicit

In other words:

1. oportet means it is proper / it is necessary / one ought
2. It often takes another infinitive to say what ought to happen
3. Since the whole thing is being reported after dicit, oportet becomes the infinitive oportere

So:

• direct: infanti tantum pirum dari oportet
• reported after dicit: infanti tantum pirum dari oportere

Here tantum means only or just.

It limits pirum:

• tantum pirum = only a pear, just a pear

So the contrast is:

• nuces bonas esse = nuts are good
• sed infanti tantum pirum dari oportere = but only a pear ought to be given to the child

In other contexts tantum can mean so much or so greatly, but here only is clearly the right sense.

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

So the important things are the forms:

• avia = nominative subject
• nuces = accusative in indirect statement
• bonas agrees with nuces
• infanti = dative
• pirum = accusative with dari oportere

That said, the word order is still meaningful stylistically:

• nuces bonas keeps noun and adjective together
• infanti comes early, giving prominence to the child
• tantum pirum keeps only close to the word it limits
• dari oportere comes at the end, where Latin often places verbal ideas

So the order is flexible, but not meaningless.