Hoc negotium magnum est, itaque mater ad forum festinat.

Because negotium is a neuter singular noun, and the demonstrative hic, haec, hoc must agree with it in gender, number, and case.

So here:

• hoc = this (neuter singular nominative)
• negotium = business / matter / task (neuter singular nominative)

They match, so hoc negotium means this business or this matter.

For the same reason: magnum must agree with negotium.

• negotium is neuter singular nominative
• so the adjective must also be neuter singular nominative
• therefore: magnum

Compare:

• magnus = masculine singular
• magna = feminine singular
• magnum = neuter singular

So hoc negotium magnum est literally means this business is big/great.

Here negotium is nominative singular, because it is the subject of est.

The structure is:

• hoc negotium = the subject
• magnum = predicate adjective describing the subject
• est = is

In sentences with to be (esse), the subject is in the nominative, and the predicate adjective also agrees with it.

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

So:

• mater can mean mother, a mother, or the mother
• forum can mean forum, the forum, or a forum
• negotium can mean business, the business, a matter, etc.

You figure out which is best from the context.

Negotium is a very common Latin word with a range of meanings, such as:

• business
• matter
• task
• affair
• problem

So hoc negotium magnum est could mean something like:

• This is an important matter
• This business is serious
• This task is big

The exact shade of meaning depends on context.

Itaque means and so, therefore, or so.

It connects the two ideas:

• Hoc negotium magnum est = this is an important/big matter
• itaque mater ad forum festinat = therefore mother hurries to the forum

So it shows result: because the matter is important, the mother hurries to the forum.

Because mater is the subject of festinat, so it must be in the nominative case.

• mater = nominative singular, mother
• matrem = accusative singular, mother as a direct object

Here the mother is the one doing the action of hurrying, so Latin uses mater.

Because ad means to or toward, and it is commonly used with the accusative to show motion toward a place.

So:

• ad forum = to the forum

This is a very common Latin pattern:

• ad urbem = to the city
• ad villam = to the house/farm
• ad forum = to the forum

Without ad, forum by itself would not normally express to the forum in basic prose.

Because ad takes the accusative case.

So:

• forum here is accusative singular
• the dictionary form is also forum, since it is a second-declension neuter noun

That can be confusing at first, because for many neuter second-declension nouns:

• nominative singular = forum
• accusative singular = forum

The form looks the same, but the function is different. Here it is accusative because it follows ad.

Festinat is present tense, third person singular, from festinare = to hurry.

So it means:

• he hurries
• she hurries
• it hurries

Here the subject is mater, so the natural translation is mother hurries or the mother is hurrying.

We know from both the noun and the verb:

• mater = singular
• festinat = third person singular

If the subject were plural, you would expect something like matres festinant:

• matres = mothers
• festinant = they hurry

Latin often makes number very clear through verb endings.

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

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

• Mater itaque ad forum festinat.
• Itaque mater festinat ad forum.
• Ad forum mater itaque festinat.

However, the original order is natural and clear. Word order in Latin often affects emphasis, not just grammar.

For example:

• Hoc negotium magnum est puts hoc negotium first, making the matter itself prominent.
• Itaque mater ad forum festinat then gives the consequence.

Latin often places esse forms (est, erat, etc.) later in the clause, and predicate adjectives commonly come before them.

So:

• hoc negotium magnum est

is a very normal Latin order.

English prefers This business is big, but Latin often likes:

• subject
• description
• est

This is one of the many places where Latin word order does not match English word order exactly.

Yes. Magnus, magna, magnum can mean:

• big
• large
• great
• important

In a sentence like Hoc negotium magnum est, important or serious may fit better than physically big, since negotium is an abstract thing.

So a learner should not always translate magnus mechanically as only big.

In Roman life, the forum was a central public space used for things like:

• business
• law
• politics
• meetings
• shopping

So mater ad forum festinat suggests she is hurrying to an important public place, probably because this negotium needs attention there.

That cultural background helps the sentence feel more natural.