Mater dicit puteum altum esse, sed ancillam aquam facile haurire posse.

Because Latin uses the accusative + infinitive construction for indirect statement after verbs like dicit.

So instead of saying:

• Mater dicit quod puteus altus est
  (not the normal classical construction)

Latin says:

• Mater dicit puteum altum esse

Here:

• puteum = the logical subject of esse
• but it goes into the accusative because it is the subject of an infinitive in indirect statement

A native English speaker often expects a normal finite clause after says that..., but Latin usually prefers this different structure.

Altum agrees with puteum.

Since puteum is:

• masculine
• singular
• accusative

the adjective describing it must also be:

• masculine
• singular
• accusative

So:

• puteus altus = the deep well / the well is deep in a direct statement setting
• puteum altum esse = that the well is deep in indirect statement

The adjective changes case to match the noun.

Because esse is the infinitive of sum, and an indirect statement after dicit normally uses an infinitive.

So:

• direct statement: Puteus altus est = The well is deep
• indirect statement: Mater dicit puteum altum esse = Mother says that the well is deep

English keeps a finite verb: is.
Latin changes it to an infinitive: esse.

For the same reason that puteum is accusative: it is the subject of an infinitive in indirect statement.

In the second part, the understood structure is:

• Mater dicit ancillam aquam facile haurire posse

So ancillam is the one who is able to draw water, but because this is still part of what Mater dicit, Latin puts ancillam in the accusative.

They have different jobs:

• ancillam = subject of the infinitives haurire posse
• aquam = direct object of haurire

So the sense is:

• ancillam ... haurire posse = that the slave-girl can draw
• aquam haurire = to draw water

This is a very common point of confusion for English speakers, because English usually marks subject and object mostly by word order, while Latin can mark both with case and construction.

A useful way to read it is:

• ancillam = who is doing it?
• aquam = what is being drawn?

Because posse means to be able, and it normally takes another infinitive with it.

So:

• haurire = to draw
• posse = to be able
• haurire posse = to be able to draw

Then the whole phrase becomes part of indirect statement after dicit:

• ancillam aquam facile haurire posse = that the slave-girl can draw water easily

So the roles are:

• posse = infinitive required by indirect statement
• haurire = infinitive completing the meaning of posse

Because Latin can let one verb govern two coordinated clauses.

So the sentence means:

• Mater dicit puteum altum esse
• sed [dicit understood] ancillam aquam facile haurire posse

In other words, dicit applies to both parts, even though it is only written once.

This is very natural in Latin and in English too:

• Mother says that the well is deep, but that the maidservant can draw water easily.

We do not need to repeat says in English either.

Facile is an adverb meaning easily, and it modifies the verbal idea haurire posse.

In practice, the main sense is that the maidservant can draw water easily.

Most naturally, you can think of it as going especially with haurire:

• aquam facile haurire = to draw water easily

But since posse + infinitive acts as a unit, it can also be understood with the whole phrase:

• to be able easily to draw water

Either way, the meaning is basically the same here.

Because classical Latin usually does not use a conjunction equivalent to English that after verbs of saying, thinking, knowing, and so on.

English says:

• Mother says that the well is deep

Latin usually says:

• Mater dicit puteum altum esse

So instead of:

• a conjunction like that
• plus a normal finite clause

Latin uses:

• an accusative subject
• plus an infinitive verb

This is one of the biggest structural differences between Latin and English.

The word order here is quite normal, but Latin is more flexible than English.

The sentence is arranged as:

• Mater dicit
• puteum altum esse
• sed
• ancillam aquam facile haurire posse

A learner can break it into chunks like this:

1. Mater dicit = main verb
2. puteum altum esse = first indirect statement
3. sed = contrast
4. ancillam aquam facile haurire posse = second indirect statement

Latin could rearrange parts for emphasis, but this order is clear and readable. A good strategy is not to translate word-by-word in strict order, but to identify each grammatical unit.

Both esse and posse are present infinitives, and haurire is also a present infinitive.

In indirect statement, the present infinitive usually shows action or state that is simultaneous with the main verb.

So:

• Mater dicit puteum altum esse = Mother says that the well is deep
• Mater dicit ancillam aquam facile haurire posse = Mother says that the maidservant can draw water easily

The idea is not past or future; it is current at the time of dicit.

They are:

• dicit from dico, dicere, dixi, dictum = say
• esse from sum, esse, fui, futurus = be
• haurire from haurio, haurire, hausi, haustum = draw, draw up
• posse from possum, posse, potui = be able

A learner may especially want to remember that:

• posse is an irregular infinitive
• it comes from possum
• it often appears with another infinitive, as in haurire posse

So recognizing posse quickly is very helpful.