“Fortior” comparativus est, “fortissimus” autem superlativus.

They both come from the adjective fortis, which means strong, brave, or courageous depending on context.

• fortior = the comparative form, meaning stronger / braver
• fortissimus = the superlative form, meaning strongest / bravest

So the sentence is identifying the degree of each adjective form.

In Latin, the comparative degree is the form used when something is more of a quality than something else.

For example:

• fortis = strong
• fortior = stronger

So fortior is called comparativus because it is the comparative form of fortis.

The superlative degree expresses the highest degree of a quality.

For example:

• fortis = strong
• fortior = stronger
• fortissimus = strongest

So fortissimus is superlativus because it is the superlative form.

They are formed in the regular Latin way for many adjectives:

• fortis → fortior for the comparative
• fortis → fortissimus for the superlative

A simple way to think of it is:

• comparative often uses -ior for masculine/feminine and -ius for neuter
• superlative often uses -issimus, -issima, -issimum

So from fortis you get:

• masculine/feminine comparative: fortior
• neuter comparative: fortius
• masculine superlative: fortissimus
• feminine superlative: fortissima
• neuter superlative: fortissimum

That is the regular superlative ending for many adjectives, especially adjectives like fortis.

So:

• stem: fort-
• superlative ending: -issimus

This gives fortissimus.

The double s is not unusual here; it is simply part of the normal superlative formation.

They are nominative singular masculine.

In this sentence they are being used as predicate words after est:

• fortior comparativus est
• fortissimus autem superlativus

In effect, they mean is comparative and is superlative.

You can think of comparativus and superlativus as adjectives used almost like nouns in grammar terminology: the comparative and the superlative.

They are masculine singular because Latin grammar terms like this are often understood with an implied masculine noun such as gradus (degree).

So the full idea is something like:

• fortior comparativus [gradus] est
• fortissimus autem superlativus [gradus est]

That is, fortior is the comparative degree and fortissimus the superlative degree.

Even if gradus is not written, it helps explain the masculine singular form.

Because autem is a postpositive word in Latin. That means it usually comes second in its clause, not first.

So Latin prefers:

• fortissimus autem superlativus

rather than putting autem at the very front.

Here autem means something like however, moreover, or on the other hand, marking a contrast between the two forms.

The first clause says:

• fortior comparativus est

The second clause is:

• fortissimus autem superlativus

Latin very often omits a word when it is easily understood from the previous clause. So the second est is understood but not written.

The full version would be:

• fortior comparativus est, fortissimus autem superlativus est

This omission is very common in Latin.

Yes. Fortior is the nominative singular comparative form for both masculine and feminine.

So it can mean:

• stronger (masculine)
• stronger (feminine)

The neuter nominative singular form would be fortius.

In this sentence, though, fortior is simply being cited as a grammatical form, not used to describe a specific person or thing.

Because Latin has no definite article and no indefinite article.

So Latin does not have separate words for:

• the
• a
• an

That means comparativus can mean:

• comparative
• the comparative

and superlativus can mean:

• superlative
• the superlative

The exact English wording depends on context.

The word order is natural, but Latin word order is more flexible than English word order.

The sentence is arranged as:

• fortior | comparativus | est
• fortissimus | autem | superlativus

This puts the forms being discussed first: fortior and fortissimus. That makes sense, because the sentence is about identifying those two words.

English usually relies heavily on word order, but Latin relies much more on endings. So Latin can vary the order without changing the basic meaning.

The three degrees are:

• positive: fortis = strong / brave
• comparative: fortior = stronger / braver
• superlative: fortissimus = strongest / bravest

So this sentence gives the second and third members of that set.

The full idea is:

• fortis = positive
• fortior = comparative
• fortissimus = superlative