Haec sententia omnium difficillima est.

Yes. Here haec means this.

It is the feminine nominative singular form of the demonstrative hic, haec, hoc (this). It has to match sententia, which is feminine singular nominative.

So:

• haec = this
• sententia = sentence
• together: this sentence

Because sententia is a feminine noun.

In Latin, demonstratives like this must agree with the noun they describe in:

• gender
• number
• case

Since sententia is feminine singular nominative, the correct form is haec, not hic.

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

It is nominative singular.

You can tell because it is the subject of the sentence: it is the thing being described as most difficult.

Also, the endings fit:

• sententi-a: nominative singular feminine, first declension
• haec: nominative singular feminine, agreeing with sententia

So haec sententia is the subject: this sentence.

Not always.

Sententia can mean several related things, depending on context, such as:

• sentence
• opinion
• view
• judgment
• thought

In this sentence, it is understood as sentence, but in other contexts it might mean opinion or judgment instead.

That is very common in Latin: one word can have a wider range of meanings than its usual English translation.

Because Latin often uses the genitive with a superlative to mean of all.

So:

• difficillima = most difficult
• omnium = of all

Together, omnium difficillima means the most difficult of all.

This is a standard Latin construction. The genitive here is sometimes called the genitive of the whole or partitive genitive.

It is the genitive plural of omnis, omne, meaning all or every.

Its forms include:

• nominative singular masculine/feminine: omnis
• nominative singular neuter: omne
• genitive singular: omnis
• nominative plural masculine/feminine: omnes
• nominative plural neuter: omnia
• genitive plural: omnium

So omnium literally means of all.

Yes. Difficillima is the superlative form of difficilis, meaning difficult.

So the degrees are:

• difficilis = difficult
• difficilior = more difficult
• difficillima = most difficult

More precisely, difficillima here is:

• feminine
• nominative singular

It agrees with sententia, which is also feminine nominative singular.

Because difficilis belongs to a small group of adjectives whose superlative is formed with -illimus, -illima, -illimum rather than the more common -issimus pattern.

So:

• difficilis → difficillimus / difficillima / difficillimum
• facilis → facillimus
• similis → simillimus

This is something you mainly have to learn as a vocabulary pattern.

So difficillima is the correct Latin form here.

Because it describes sententia.

In Latin, adjectives agree with the nouns they describe in:

• gender
• number
• case

Since sententia is feminine singular nominative, difficillima must also be feminine singular nominative.

That is why the sentence has:

• haec sententia
• omnium difficillima

Everything describing sententia matches it.

Yes, that is normal.

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

So Haec sententia omnium difficillima est can place est at the end without causing confusion.

Putting est last is very common in Latin, especially in simple equational sentences like this one.

The order here also gives a nice emphasis:

• This sentence
• of all, most difficult
• is

In smoother English, of course, we say This sentence is the most difficult of all.

Yes, often they could.

For example, Latin could also say things like:

• Haec sententia est omnium difficillima
• Omnium difficillima haec sententia est

The basic meaning would stay the same because the endings still show what goes with what.

However, a different order can change the emphasis or style. The given order highlights omnium difficillima before the final est.

Yes, that is the natural understanding.

Latin often leaves something unstated when it is obvious from context. So omnium by itself means of all, but in context it means something like:

• of all sentences
• or out of all of them

Since the subject is this sentence, the comparison is naturally with other sentences.

If Latin wanted to state it more explicitly, it could say omnium sententiarum = of all sentences.

Yes, haec can be ambiguous when you look at it by itself.

It can be:

• feminine nominative singular = this
• neuter nominative or accusative plural = these

But in this sentence there is no real ambiguity, because haec is clearly agreeing with sententia, which is singular feminine.

So here it definitely means this, not these.

A good way is to break it into pieces:

• Haec sententia = this sentence
• omnium = of all
• difficillima = most difficult
• est = is

Then reorder it into natural English:

This sentence is the most difficult of all.

So the core pattern is:

subject + superlative expression + est

That is a very common Latin sentence type.

In a classical pronunciation, roughly:

haik sen-TEN-ti-a OM-ni-um dif-fi-KIL-li-ma est

A few helpful points:

• ae in haec sounds like the ai in aisle
• c is always hard, so haec ends with a k sound
• ti in sententia is usually pronounced as ti, not like English sh
• the stress is on -TEN- in sententia
• the stress is on -KIL- in difficillima

You do not need perfect pronunciation to understand the grammar, but these are the main features.