Opera ancillae matri magno auxilio est.

The sentence breaks down like this:

• opera ancillae = the subject
• matri = the person affected or benefited
• magno auxilio = the purpose or function
• est = is

So grammatically it is:

[subject] + [dative of person] + [dative of purpose] + est

This is a very common Latin pattern with esse.

Here opera is singular, not plural.

It is the nominative singular of opera, operae, a first-declension noun. In this sentence it is the subject of est.

A beginner might confuse it with opera as the neuter plural of opus, but that is not what is happening here. The singular verb est helps show that the sentence is talking about one thing, not several.

The form ancillae is ambiguous by itself. It could be:

• genitive singular = of the maidservant
• dative singular = to/for the maidservant
• nominative plural = maidservants

Here it is understood as genitive singular, because it most naturally goes with opera:

• opera ancillae = the work/service/help of the maidservant

The meaning you have already been shown tells you which interpretation is intended. Latin often relies on context to resolve forms like this.

Matri is dative singular of mater.

It marks the person to whom or for whom something is helpful. So matri means:

• to the mother
• for the mother

English usually uses a preposition here, but Latin often uses the dative case instead.

That is because this is a special Latin idiom.

In English, after is, we often expect a nominative idea, as in This is a help. But Latin very often says:

• alicui auxilio esse = to be a help to someone

Here auxilio is in the dative case, called the dative of purpose.

So magno auxilio est means literally something like:

• is for a great help

But in natural English we usually say:

• is a great help

Yes.

This sentence has two datives:

• matri = dative of reference/advantage, the person concerned
• magno auxilio = dative of purpose, the function served

So the pattern is:

• something + person in the dative + purpose in the dative + est

Very literally:

• The maidservant’s work is to the mother for great help

Better English:

• The maidservant’s work is a great help to the mother

Because in this construction auxilio is dative, not nominative or accusative.

Since auxilio is:

• singular
• dative
• neuter

the adjective agreeing with it must also be:

• singular
• dative
• neuter

That gives magno.

So:

• magno auxilio = for great help / as a great help

If Latin were using a regular predicate noun instead, you might expect magnum auxilium, but that is not the construction here.

Because magno goes with auxilio, not with matri.

You can tell by the endings:

• matri is feminine dative singular
• auxilio is neuter dative singular
• magno is neuter dative singular

So magno auxilio is a unit:

• as a great help
• for great help

Classical Latin does not have articles like English the or a/an.

So a Latin noun like mater or ancilla can mean:

• mother
• the mother
• a mother

The exact sense comes from context.

That is why matri can naturally be understood as to the mother, even though there is no separate word for the.

Yes. Latin word order is much freer than English word order because the case endings show the grammatical relationships.

So this sentence could be rearranged in several ways without changing the core meaning, for example:

• Ancillae opera matri magno auxilio est
• Matri opera ancillae magno auxilio est

The version you have puts opera first, which gives it some prominence, and places est at the end, which is very common in Latin.

In isolation, a learner might wonder about that, because Latin word order is flexible and ancillae is form-ambiguous.

So yes, purely as a form, you might ask whether it could be connected differently. But if the meaning has already been given, that settles the intended reading.

In the intended reading here, ancillae goes with opera:

• opera ancillae = the maidservant’s work/service/help

This is a good example of how Latin sometimes requires you to use both endings and context together.