Matri nihil refert utrum infans lac an aquam bibat, dummodo satis bibat.

Because Latin commonly uses the dative with expressions like refert to show to whom something matters.

So:

• matri = to the mother / for the mother
• nihil refert = it matters not at all / it makes no difference

Literally, the first part is something like:

• To the mother it matters nothing...

This is more natural Latin than trying to make mater the subject.

Although referre can mean to bring back or to report in other contexts, in this idiom refert means it matters or it makes a difference.

So:

• quid refert? = what does it matter?
• nihil refert = it matters not at all
• multum refert = it matters a great deal

This is a fixed idiomatic use, and learners usually just need to memorize it as such.

utrum ... an ... is the standard way to introduce an indirect question meaning whether ... or ...

So:

• utrum infans lac an aquam bibat = whether the baby drinks milk or water

This is not just a simple or joining two nouns. It sets up two alternatives inside a clause:

• utrum = whether
• an = or

Latin often uses utrum ... an ... where English uses whether ... or ...

Because utrum ... an ... here introduces an indirect question, and indirect questions in Latin normally take the subjunctive.

So in:

• utrum infans lac an aquam bibat

the verb bibat is subjunctive because the whole clause depends on refert:

• It makes no difference whether the baby drinks milk or water

This is a very common rule in Latin:

• direct question: infansne lac bibit? = Is the baby drinking milk?
• indirect question: rogat utrum infans lac bibat = He asks whether the baby is drinking milk

Yes, that is what it means, but Latin often uses one verb for both alternatives when the same verb applies to both.

So:

• utrum infans lac an aquam bibat

means:

• whether the baby drinks milk or water
• literally, whether the baby drinks milk or water-drinks

English does the same thing:

• I don’t know whether he bought bread or wine

We do not need to repeat bought after both nouns.

Because the two nouns belong to different declensions and have different accusative forms.

Here both lac and aquam are objects of bibat, so both are accusative.

• lac is a neuter third-declension noun, and its nominative and accusative singular are the same: lac
• aqua is a first-declension feminine noun, whose accusative singular is aquam

So:

• lac = accusative singular
• aquam = accusative singular

This is a very common thing in Latin: neuter nouns often have the same form in nominative and accusative.

Infans is nominative singular here, and it is the subject of bibat.

So the structure is:

• infans = subject
• lac / aquam = direct object
• bibat = verb

Even though infans can have the same form in nominative and accusative singular, the sentence structure and meaning make it clear that it is the subject:

• whether the baby drinks milk or water

not

• whether milk or water drinks the baby

Dummodo means provided that, so long as, or as long as only.

So:

• dummodo satis bibat = provided that he/she drinks enough

It introduces a condition, but not the ordinary kind you see with si. It often has the sense of I don’t care about the other details, as long as this condition is met.

That fits the whole sentence very well:

• It makes no difference to the mother whether the baby drinks milk or water, provided that the baby drinks enough.

Because dummodo regularly takes the subjunctive.

So:

• dummodo ... bibat = provided that ... drinks

This is another construction that learners usually memorize as a pattern:

• dummodo
  • subjunctive = provided that / so long as

The subjunctive here does not mean doubt in the English sense; it is simply the normal Latin grammar after dummodo.

The present subjunctive fits the general, ongoing sense of the statement.

The sentence is not talking about one specific past event. It means something like:

• It does not matter whether the baby drinks milk or water, as long as the baby drinks enough

That is a general present idea, so the present subjunctive is natural in both subordinate clauses:

• utrum ... bibat
• dummodo ... bibat

Satis means enough or sufficiently.

Here it goes with bibat:

• satis bibat = drinks enough

English can say either:

• drinks enough
• drinks sufficiently

Latin satis is very common in this kind of expression.

Not in the same way.

In utrum ... an ..., an is the normal partner of utrum in a whether ... or ... construction.

So:

• utrum ... an ... = whether ... or ...

By contrast:

• aut and vel are ordinary coordinating words for or
• they do not normally replace an in this indirect-question pattern

So a learner should recognize utrum ... an ... as a special set phrase.

Yes, Latin word order is flexible, but this order is natural and clear.

The sentence begins with matri, which highlights the person whose point of view matters:

• To the mother, it makes no difference...

Then comes the impersonal expression:

• nihil refert

Then the indirect question:

• utrum infans lac an aquam bibat

And finally the condition:

• dummodo satis bibat

So the order helps the sentence unfold logically:

1. whose concern?
2. what is the judgment?
3. between what alternatives?
4. under what condition?

Latin could rearrange these elements, but this version is elegant and easy to follow.

Infans literally means infant, baby, or young child.

Grammatically, it is a common-gender noun: it can refer to a male or female child depending on context. The sentence does not specify sex.

That is why English translations may say:

• the baby
• the infant
• he/she

The Latin itself stays neutral about that detail.

It is not awkward in Latin. In fact, the repetition is helpful because the two clauses are doing different jobs:

• utrum ... bibat = indirect question
• dummodo ... bibat = condition/proviso

The first bibat asks about the kind of drink. The second bibat states the important requirement.

So the repetition actually reinforces the meaning:

• the type of drink does not matter
• the amount drunk does matter