Sol hodie clarior est quam heri.

Because the sentence is making a comparison: the sun is brighter than it was yesterday.

• clarus = bright, clear
• clarior = brighter, clearer

In Latin, the comparative form is often made by adding -ior (masculine/feminine) or -ius (neuter) to the adjective stem.

So:

• clarus = bright
• clarior = brighter
• clarissimus = brightest / very bright

Here, clarior is correct because the sentence compares today with yesterday.

Quam means than in comparisons.

So:

• clarior quam heri = brighter than yesterday

It links the comparative adjective clarior with the thing being compared.

A very common Latin pattern is:

• comparative adjective + quam = more/er ... than

For example:

• maior quam = bigger than
• celerior quam = faster than
• clarior quam = brighter than

Because heri is already an adverb meaning yesterday.

English says than yesterday, and Latin can do the same idea with:

• quam heri = than yesterday

There is no extra ending needed here because heri is not a noun like the day of yesterday; it is simply an adverb of time.

So the comparison is understood as:

• The sun is brighter today than it was yesterday.

Latin often leaves parts implied when the meaning is obvious.

Because the sentence contrasts today and yesterday.

• hodie = today
• heri = yesterday

So the full idea is:

• Sol hodie clarior est quam heri.
• The sun is brighter today than yesterday.

Without hodie, the sentence would still be possible in some contexts, but adding it makes the contrast explicit and natural.

Est means is.

Latin often does express the verb to be, especially in straightforward statements like this one:

• Sol ... clarior est = The sun is brighter

In some contexts, especially poetry or very compressed style, Latin may omit forms of esse when they are easy to supply. But in ordinary prose, est is completely normal and expected here.

Clarior is in the nominative singular masculine because it agrees with sol.

• sol = sun
• sol is masculine singular nominative
• the predicate adjective describing it must match that

So:

• sol ... clarior est = the sun is brighter

Even though clarior comes after hodie, it still describes sol and must agree with it in gender, number, and case.

Sol is a noun meaning sun.

Its dictionary form is usually given as:

• sol, solis (masculine)

It is a third-declension masculine noun.

In this sentence, sol is the subject, so it appears in the nominative singular:

• Sol ... est = The sun is ...

Either can be possible depending on context, because clarus has a range of meanings including clear, bright, and sometimes famous in other contexts.

With sol, the most natural English meaning is usually:

• brighter

So:

• Sol hodie clarior est quam heri.
• The sun is brighter today than yesterday.

A learner should remember that Latin words often cover a wider range of meanings than a single English word.

Yes. Latin word order is much more flexible than English word order because the endings show how words relate to each other.

This sentence could be rearranged in several ways without changing the basic meaning, for example:

• Hodie sol clarior est quam heri.
• Sol clarior hodie est quam heri.

The given order is natural and clear:

• Sol sets up the subject
• hodie gives the time
• clarior gives the main description
• est completes the statement
• quam heri adds the comparison

Latin word order often reflects emphasis and style, not just grammar.

In theory, Latin can sometimes use magis + adjective for more ..., but with ordinary adjectives like clarus, Latin normally prefers the built-in comparative form:

• clarior = brighter

So clarior is the usual and idiomatic choice.

Using magis clarus here would sound less standard than the simple comparative.

Yes. It is understood as something like:

• quam heri erat
• than it was yesterday

Latin often leaves out repeated words when they are easy to understand from context.

So instead of saying the whole thing, Latin simply says:

• clarior est quam heri

The omitted idea is natural and does not cause confusion.