Haec via ad forum brevissima est.

Because haec has to agree with via.

The noun via is:

• feminine
• singular
• nominative

So the demonstrative adjective must also be feminine singular nominative. In the hic, haec, hoc set, that form is haec.

So:

• hic = masculine nominative singular
• haec = feminine nominative singular
• hoc = neuter nominative singular

Since the sentence is about this road, Latin uses haec via.

Via is nominative singular.

We know this because it is the subject of the sentence: the road is what the sentence is talking about. In a sentence with est, the subject is normally in the nominative.

So in Haec via ad forum brevissima est, haec via means this road and functions as the subject.

Because brevissima is describing via, and adjectives in Latin must agree with the nouns they describe in:

• gender
• number
• case

Since via is feminine singular nominative, brevissima must also be feminine singular nominative.

Its dictionary form would be based on brevis, breve = short.
The superlative is:

• brevissimus = masculine
• brevissima = feminine
• brevissimum = neuter

So brevissima matches via correctly.

It can mean either, depending on context.

As a superlative, brevissima literally means shortest. But Latin superlatives can also sometimes mean very short rather than strictly the shortest.

So this form may be understood as:

• the shortest
• or very short

The surrounding context usually makes it clear which sense is intended.

Ad forum means to the forum or toward the forum.

The preposition ad commonly takes the accusative case and often expresses:

• motion toward
• direction
• relation such as to or for

Here it tells you where the road leads: to the forum.

So:

• ad = to, toward
• forum = the object of ad

Because ad requires the accusative case.

That is a standard Latin rule: some prepositions take specific cases, and ad takes the accusative.

So in ad forum, forum is accusative because it is the object of the preposition ad.

There is one extra detail that often confuses learners: forum is a neuter second-declension noun, and in neuter nouns the nominative singular and accusative singular look the same. So although forum is accusative here, it looks identical to the nominative form.

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

So Latin simply says forum, and English has to decide whether to translate it as:

• the forum
• a forum
• or just forum

In this sentence, English naturally uses the forum, even though Latin does not have a separate word for the.

Latin word order is much more flexible than English word order because the endings show the grammatical relationships.

Putting est at the end is very normal Latin style. It does not change the basic meaning. The sentence could be rearranged in other ways, but Haec via ad forum brevissima est is perfectly natural.

Latin often places the verb later in the sentence, especially in simple descriptive statements like this one.

Yes, often they could.

Because Latin uses case endings, the grammar does not depend as heavily on position as English does. For example, forms such as these would still be understandable:

• Haec brevissima via ad forum est
• Ad forum haec via brevissima est
• Brevissima est haec via ad forum

The emphasis may shift slightly depending on the order, but the core meaning remains the same.

By context and agreement.

The form haec can be more than one thing in Latin. For example, it can also be neuter plural nominative/accusative. But here it is followed by via, which is feminine singular nominative. That tells us haec must also be feminine singular nominative.

So here haec via clearly means this road.

Yes. Via is a very common Latin noun meaning road, way, or street.

It is a first-declension feminine noun. Its basic forms are:

• nominative singular: via
• genitive singular: viae

That is why forms agreeing with it, like haec and brevissima, are feminine in this sentence.