Lucia hodie plus quam Marcus legit.

Because Latin word order is much freer than English word order. The endings on words usually show what each word is doing, so Latin does not rely on position as heavily as English does.

Putting the verb at the end is very common in Latin, especially in straightforward prose. So Lucia hodie plus quam Marcus legit is a very normal way to say it.

That said, Latin could move the words around for emphasis, for example:

• Hodie Lucia plus quam Marcus legit
• Lucia plus quam Marcus hodie legit

The basic meaning would stay the same, though the emphasis might shift a little.

Marcus is nominative.

It is nominative because it is understood as the subject of an omitted verb:

• Lucia hodie plus quam Marcus legit
• literally: Lucia reads more than Marcus [reads] today

So Marcus is not the object of anything here. He is the person Lucia is being compared with, and in the full underlying sense he would also be the subject of legit.

Yes. Latin often leaves out a word when it is easy to understand from context. This is called ellipsis.

So the sentence really means:

• Lucia hodie plus quam Marcus legit
• Lucia reads more today than Marcus [reads]

Latin does this very naturally, just as English does in sentences like Lucia reads more than Marcus.

Here plus means more.

It is working adverbially with the verb legit, so the sense is reads more or does more reading.

That is different from using a comparative adjective with a noun. For example:

• plures libros = more books

But in your sentence, the comparison is about the action of reading, not directly about a noun, so plus is the natural word.

Yes. In this sentence, plus ... quam ... is the normal pattern for more ... than ....

• plus = more
• quam = than

So:

• plus quam Marcus = more than Marcus

The word quam introduces the standard of comparison, just as than does in English.

Sometimes magis can also mean more, but plus is very natural here.

A useful guideline is:

• magis is often used with adjectives and adverbs: more beautiful, more quickly
• plus is often used for more in amount or degree, especially with verbs or in a more substantive sense

So plus legit = reads more is a normal Latin expression.

Not necessarily. Latin, like English, can leave the object unstated when it is obvious or unimportant.

English does this too:

• Lucia reads more than Marcus

That does not have to mean reads more books specifically. It can just mean does more reading.

If Latin wanted to be more specific, it could add an object, for example:

• Lucia hodie plures libros quam Marcus legit = Lucia reads more books today than Marcus

But your sentence is perfectly fine without an explicit object.

Without macrons, legit can be ambiguous in writing.

It can represent:

• legit = reads (present tense)
• lēgit = read / has read (perfect tense)

In many printed Latin texts, macrons are omitted, so context has to tell you which meaning is intended.

In this sentence, the present meaning reads is the most natural interpretation, especially because of the overall sense of the sentence. But technically, if macrons are not written, the form is ambiguous on the page.

Hodie means today, and it is an adverb modifying legit.

It tells you when Lucia reads more than Marcus.

Yes, it could be placed elsewhere. Latin adverbs are often movable:

• Lucia hodie plus quam Marcus legit
• Hodie Lucia plus quam Marcus legit
• Lucia plus quam Marcus hodie legit

These all mean basically the same thing, though the emphasis may differ a little.

Because Latin does not have articles like English the and a/an.

So Latin often just uses the noun by itself:

• Lucia = Lucia
• Marcus = Marcus

Whether English should use the, a, or no article at all depends on the translation and context, not on a separate Latin word.

You know it from both meaning and form.

• Lucia is a nominative singular proper noun
• legit is third person singular
• Marcus is also nominative, but in this construction he belongs with quam and is understood as the subject of the omitted second verb

So the main clause is:

• Lucia ... legit = Lucia reads

Then quam Marcus adds the comparison:

• than Marcus [does]

So Lucia is the subject of the stated verb, and Marcus is the subject of the implied verb.