Haec arbor altior est quam illa.

Haec is the feminine nominative singular form of the demonstrative hic, haec, hoc meaning this.

It is feminine singular here because it agrees with arbor, which is:

• feminine
• singular
• nominative (the subject)

So haec arbor means this tree.

A learner often expects one Latin word for this, but Latin changes the form depending on:

• gender
• number
• case

So you get forms like:

• hic = this (masculine)
• haec = this (feminine)
• hoc = this (neuter)

Latin noun gender often has to be learned with the noun; it is not always predictable from the English meaning or from the ending.

Arbor, arboris is a third-declension feminine noun, so it is grammatically feminine even though a tree is not biologically female.

That matters because any adjective or demonstrative connected with arbor must match it in gender, number, and case. That is why you see:

• haec arbor
• altior (agreeing with arbor)

Altior is the comparative form of the adjective altus, alta, altum.

So:

• altus = tall / high / deep
• altior = taller / higher

Latin usually forms the comparative in one word instead of using a separate word like more.

So where English says:

• taller

Latin says:

• altior

In this sentence, altior is describing arbor.

This is a very common question.

In the comparative, the nominative singular masculine and feminine forms are the same.

So:

• masculine nominative singular: altior
• feminine nominative singular: altior
• neuter nominative singular: altius

That means altior can be either masculine or feminine depending on the noun it goes with. Here it is feminine because it agrees with arbor.

Quam means than in a comparison.

So altior ... quam illa means taller ... than that one.

Latin commonly uses:

• comparative adjective + quam

For example:

• maior quam... = bigger than...
• celerior quam... = faster than...
• altior quam... = taller than...

Because Latin often leaves out a noun when it is obvious from the context.

Here illa means that one or, more fully, that tree. The noun arbor is understood.

So:

• haec arbor = this tree
• illa = that one / that tree

This is very natural in Latin, just as English can say:

• This tree is taller than that one

instead of repeating:

• This tree is taller than that tree

Illa is from the demonstrative ille, illa, illud, which usually means that.

Just like haec, it changes form to match gender, number, and case.

Here illa is feminine singular because it stands for illa arbor:

• feminine
• singular
• nominative in the comparison

So the contrast is:

• haec = this
• illa = that

Est is the third-person singular of esse, meaning is.

So the structure is:

• haec arbor = subject
• altior = predicate adjective
• est = is
• quam illa = than that one

Latin sometimes omits forms of to be, especially in poetry or very compressed style, but in normal prose est is perfectly standard and expected here.

Latin words that go together must agree in certain features.

Here is the agreement:

• haec agrees with arbor

  • feminine
  • singular
  • nominative

• altior also agrees with arbor

  • feminine
  • singular
  • nominative
    (even though the form altior is the same for masculine and feminine)

• illa stands for illa arbor, so it is also feminine singular

This matching system is one of the main things that helps Latin readers understand who is doing what.

Latin word order is more flexible than English word order because the endings carry so much information.

This sentence is a very natural order:

• Haec arbor = this tree
• altior est = is taller
• quam illa = than that one

But Latin can often rearrange words for emphasis or style. Even so, the forms still show the relationships.

For a beginner, it is helpful to see the sentence as three pieces:

• Haec arbor
• altior est
• quam illa

That makes the structure much easier to recognize.