Cum mater adest, infans quietius dormit.

Because cum can be either:

• a preposition meaning with when it is followed by a noun in the ablative
• a conjunction meaning when, since, or although when it introduces a clause

Here, cum is followed by a whole clause: mater adest = the mother is present. So it is a conjunction, and the sentence means When the mother is present, the baby sleeps more quietly.

Mater is the nominative singular form, which is used for the subject of the clause.

In mater adest:

• mater = the mother → subject
• adest = is present

So mater has to be nominative because she is the one doing the action of being present.

Adest means is present, is here, or is nearby.

It comes from the verb adsum, adesse, which is built from:

• ad- = to, near
• sum = I am

So literally it has the sense of to be near or to be present.

Adest is:

• 3rd person singular
• present tense
• active
• indicative

So it means he/she/it is present. Here it refers to mater, so: the mother is present.

Because infans is also the subject of its clause, so it is in the nominative singular.

In infans quietius dormit:

• infans = the baby/infant → subject
• dormit = sleeps

So infans must be nominative, just like mater in the first clause.

Infans is a 3rd-declension noun. Its nominative singular is infans, and that form can mean infant, baby, or sometimes child.

A learner may notice that infans ends in -s, which is common in many 3rd-declension nominatives. Even though it does not look like a 1st- or 2nd-declension noun, it is still perfectly normal as a nominative singular subject.

Quietius is a comparative adverb, meaning more quietly.

It comes from quietus, -a, -um = quiet or calm.
The adverbial idea is quietly, and the comparative is more quietly.

In Latin, comparative adverbs often end in -ius, so:

• fortiter = bravely → fortius = more bravely
• clare = clearly → clarius = more clearly
• quiete / quieto modo or related adverbial sense → quietius = more quietly

So infans quietius dormit means the baby sleeps more quietly.

Latin often leaves that unstated when it is clear from context.

So quietius dormit means sleeps more quietly, but Latin does not have to say exactly than when the mother is absent or than usual. The comparison is understood from the sentence as a whole:

• When the mother is present, the baby sleeps more quietly

In natural English, we might understand:

• more quietly than otherwise
• more quietly than when she is not there

Latin frequently allows this kind of implied comparison.

Latin word order is much more flexible than English word order because Latin uses case endings to show grammatical roles.

So infans quietius dormit literally has:

• subject: infans
• adverb: quietius
• verb: dormit

Putting the verb at the end is very common in Latin, though not required. The sentence could still be understood if the words were arranged differently, but the given order is natural and idiomatic.

No. This is a straightforward temporal cum meaning when, and it takes the indicative here:

• cum mater adest

The verb adest is present indicative.

Latin does sometimes use cum with the subjunctive, especially in:

• circumstantial clauses
• causal clauses
• concessive clauses

But in a simple statement like when the mother is present, the indicative is normal.

Potentially, yes, because cum can sometimes mean when or since depending on context.

However, in this sentence, the most natural reading is when the mother is present, because it describes the situation under which the baby sleeps more quietly.

So although since is grammatically possible in some contexts, when is the best translation here.

Yes: both clauses are in the present tense, which shows a general or repeated situation:

• cum mater adest = when the mother is present
• infans quietius dormit = the baby sleeps more quietly

This sounds like a general truth or usual pattern, not a one-time event. In English, we often use the simple present the same way:

• When the mother is present, the baby sleeps more quietly.

Yes. Depending on context, good English translations could include:

• When the mother is present, the baby sleeps more quietly.
• When his mother is there, the baby sleeps more peacefully.
• The baby sleeps more quietly when the mother is present.

The Latin meaning stays the same. The main points are:

• cum = when
• mater adest = the mother is present / there
• infans = the baby
• quietius dormit = sleeps more quietly