Scriptura huius epistulae tam clara est ut avia eam facile legat.

Here scriptura means the writing or the handwriting of the letter — basically, the way it is written on the page.

It does not mean Scripture here. Although scriptura can mean writing in a broad sense, in this sentence it is being used concretely: the letter’s writing is clear and easy to read.

Because both words are in the genitive, which often shows possession or close relationship.

• epistulae = of the letter
• huius = of this

So scriptura huius epistulae means the writing/handwriting of this letter.

Because huius is the genitive singular form of hic, haec, hoc (this).

A learner often expects something like haec epistula, which would mean this letter if letter were the main noun of the phrase. But here the main noun is scriptura, and epistulae is in the genitive: of this letter.

So:

• haec epistula = this letter
• huius epistulae = of this letter

Also, huius is the same genitive singular form for masculine, feminine, and neuter.

tam ... ut is a very common Latin pattern meaning so ... that.

Here:

• tam clara = so clear
• ut avia eam facile legat = that grandmother can read it easily

So the sentence is describing a result:

• The writing is so clear
• that a certain result follows: grandmother can read it easily

It is a result clause, not a purpose clause.

Why?

Because of tam. When Latin says tam ... ut, it usually means so ... that, which expresses a result.

So this sentence does not mean:

• The writing is clear in order that grandmother may read it

It means:

• The writing is so clear that grandmother can read it

That is classic result clause usage.

Because Latin normally uses the subjunctive in a result clause introduced by ut.

So after tam clara est ut..., you expect a subjunctive verb:

• legat = present subjunctive of legere

This is not because the action is doubtful. It is simply the standard grammar of the construction.

legit would be the indicative: she reads or she is reading.

But after tam ... ut, Latin wants the subjunctive, so we get legat.

Compare:

• Avia eam legit. = Grandmother reads it.
• Tam clara est ut avia eam legat. = It is so clear that grandmother can read it.

So the difference is grammatical, not just lexical.

eam is a feminine singular accusative pronoun meaning her or it, depending on context. Here it means it.

Its case comes from its job in the clause: it is the direct object of legat.

As for what it refers to, the most natural sense is the letter — that is, grandmother can easily read it. Even though epistulae appeared earlier in the genitive, a pronoun can still refer back to that noun; the pronoun takes whatever case it needs in its own clause.

Formally, eam could match either epistula or scriptura, since both are feminine singular ideas, but the intended meaning is usually the letter or the writing of the letter as a readable object.

Because the sentence needs an adverb, not an adjective.

• facile = easily
• facilis = easy

Here facile modifies the verb legat:

• easily reads

If you used facilis, it would need to describe a noun, not the action of reading.

In this context, yes: clear, especially in the sense of easy to read or legible.

But clarus, clara, clarum can have several related meanings depending on context, such as:

• clear
• bright
• famous
• distinct

Here the idea is clearly legible handwriting, not brightness or fame.

Because avia is the subject of legat in the ut clause.

So inside ut avia eam facile legat:

• avia = the one doing the reading
• eam = the thing being read
• legat = reads / can read

Even though the sentence already has scriptura as the subject of the main clause, the subordinate clause has its own subject: avia.

Because Latin has no articles.

So Latin does not have separate words for:

• a
• an
• the

That means a word like avia can mean, depending on context:

• a grandmother
• the grandmother
• simply grandmother

English has to choose an article when translating, but Latin leaves that to context.

To an English speaker, maybe a little — but it is perfectly normal Latin.

Latin word order is much more flexible than English word order. This sentence is organized very naturally:

• Scriptura huius epistulae = topic: the writing of this letter
• tam clara est = statement about it: is so clear
• ut avia eam facile legat = result: that grandmother can easily read it

So the order helps the sentence unfold neatly, even though Latin does not depend on word order as heavily as English does.