Mater nobiscum ad forum ambulat.

Mater is the subject of the sentence, so it is in the nominative singular. The basic nominative form of this noun is mater, meaning mother.

A learner might expect the ending to change more obviously, but mater is a third-declension noun, and many third-declension nouns have nominative forms that do not follow a simple predictable pattern.

Here are a few forms:

• mater = mother, as the subject
• matrem = mother, as a direct object
• matris = of the mother

So in Mater nobiscum ad forum ambulat, mater is nominative because the mother is the one doing the walking.

Nobiscum means with us.

It is made from:

• nobis = us / to us / for us / by us, depending on context
• cum = with

With the personal pronouns me, te, se, nobis, vobis, Latin usually puts cum after the pronoun and writes it as one word:

• mecum = with me
• tecum = with you
• secum = with himself/herself/themselves
• nobiscum = with us
• vobiscum = with you all

So Latin normally says nobiscum, not cum nobis.

It is the ablative case.

The preposition cum takes the ablative, so:

• cum amico = with a friend
• cum puella = with the girl
• nobiscum = with us

Even though nobiscum is written as one word, it still contains the ablative form nobis.

Forum is in the accusative singular here.

The preposition ad usually takes the accusative and often means:

• to
• toward
• up to
• sometimes at or near, depending on context

Since forum is a second-declension neuter noun, its accusative singular is forum, which happens to look exactly like the nominative singular.

So:

• nominative: forum
• accusative: forum

That is why the form does not change visibly, even though the case has changed.

The ending -t shows that the verb is third person singular present active indicative.

That means:

• third person = he/she/it
• singular = one person
• present = is walking / walks

The subject is mater, which is she, so the verb must be singular:

• ambulo = I walk
• ambulas = you walk
• ambulat = he/she walks

So Mater ... ambulat means Mother walks or The mother is walking.

It can mean either one, depending on context.

Latin present tense often covers both:

• simple present: walks
• progressive present: is walking

So Mater nobiscum ad forum ambulat could be understood as:

• Mother walks with us to the forum
• Mother is walking with us to the forum

English makes a stronger distinction here than Latin often does.

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

So mater can mean:

• mother
• a mother
• the mother

And forum can mean:

• forum
• a forum
• the forum

Which one sounds best depends on context and on the translation chosen.

That is very normal in Latin. Learners often want a separate word for the, but Latin usually leaves that unstated.

Yes, the sentence could be arranged differently.

Latin word order is more flexible than English because the endings show how the words function. So these can all mean basically the same thing:

• Mater nobiscum ad forum ambulat.
• Mater ad forum nobiscum ambulat.
• Nobiscum mater ad forum ambulat.
• Ad forum mater nobiscum ambulat.

The original order is perfectly natural, but changing the order can shift emphasis.

For example:

• putting mater first may emphasize the mother
• putting nobiscum first may emphasize with us
• putting ad forum first may emphasize to the forum

So word order matters more for focus and style than for basic grammar.

Because the verb ending already tells you the subject is third person singular.

In English, we usually need a subject pronoun:

• She walks

But in Latin, ambulat already means he/she/it walks, so a separate pronoun is unnecessary unless you want emphasis.

Since mater is already present as the subject noun, adding a pronoun would be even less necessary.

Latin often leaves out subject pronouns when they are clear from the verb ending.

It can mean either, depending on context.

The preposition ad often expresses motion toward a destination, so ad forum usually means to the forum. But in some contexts it can feel more like toward the forum or in the direction of the forum.

In a simple sentence like this, learners will usually understand it as to the forum.

Not by itself.

Mater just means mother. Whether it is:

• my mother
• his mother
• our mother
• the mother

depends on context.

Latin can add possessive words if needed:

• mea mater = my mother
• nostra mater = our mother

But if no possessive is given, Latin often leaves that unstated and lets the context explain it.

Forum is a second-declension neuter noun.

That matters because neuter nouns have a special pattern:

• nominative singular: forum
• accusative singular: forum
• nominative plural: fora
• accusative plural: fora

So in this sentence, forum is accusative after ad, but it looks the same as the nominative because neuter nominative and accusative singular are identical.