Meridie sol calidior est quam mane.

Latin word order is much freer than English word order. Starting with meridie puts the time first and sets the scene: at midday.

The basic idea is still:

sol calidior est = the sun is warmer

Then Latin adds the time comparison around it. English often prefers The sun is warmer at midday than in the morning, but Latin can naturally foreground the time expression.

Meridie is the ablative singular of meridies, meridiei, a fifth-declension noun meaning midday or noon.

Here it is used as an ablative of time when, so Latin can say simply meridie for at midday. Latin often uses a bare ablative where English uses a preposition such as at, on, or in.

Not exactly.

• meridie is a regular ablative form of a declinable noun
• mane is an indeclinable word, often treated as a noun used adverbially, meaning in the morning or early in the morning

So even though both are time expressions, they do not have to look alike. Latin often uses different structures for words of time.

Latin has no articles. There is no separate word for the or a/an.

So sol can mean:

• the sun
• a sun

depending on context. In this sentence, it is naturally understood as the sun.

Because the sentence is making a comparison.

• calidus = warm / hot
• calidior = warmer / hotter

The sentence is not just saying that the sun is warm; it is saying that the sun is warmer than it is at another time of day.

Because calidior agrees with sol, and sol is masculine singular.

For comparative adjectives:

• masculine/feminine nominative singular: -ior
• neuter nominative singular: -ius

So:

• sol calidior est = correct, because sol is masculine
• calidius would be neuter, so it would not agree with sol

Quam introduces the second part of a comparison. After a comparative adjective like calidior, it means than.

So:

• calidior ... quam ... = warmer ... than ...

It is the standard word used to connect the two sides of the comparison.

Yes. Latin often omits words that are easy to understand from context.

The fuller sense is something like:

The sun is warmer at midday than it is in the morning.

After quam, Latin does not need to repeat the whole clause. The listener can easily supply the missing idea.

The comparison is between two times, not between two different things.

The sentence compares:

• the sun at midday
• the sun in the morning

So the idea is: the same sun is warmer at one time of day than at another.

This is a very common Latin pattern:

• sol = subject
• est = is
• calidior = predicate adjective

So sol calidior est literally means the sun is warmer.

Then meridie tells you when, and quam mane tells you than when or than at what other time.