Si femina innocens est, crimen falsum maxima iniuria est.

It has two clauses:

• Si femina innocens est = If the woman is innocent
• crimen falsum maxima iniuria est = the false charge is the greatest injustice / a false accusation is a very great injustice

So this is a straightforward if... then... type sentence, even though Latin does not need a separate word for then here.

Si is the standard Latin word for if. It introduces a condition.

So:

• si = if
• si femina innocens est = if the woman is innocent

This is a simple, real condition, so Latin uses the indicative verb est, not the subjunctive.

Because there are really two complete statements in the sentence, and each one has its own verb:

1. femina innocens est = the woman is innocent
2. crimen falsum maxima iniuria est = the false charge is the greatest injustice

Latin often can omit forms of esse (to be) in some contexts, especially in poetry or very compressed prose, but in normal clear prose it is very common to state est explicitly.

Because innocens is a third-declension adjective, and its nominative singular form is the same for masculine, feminine, and neuter.

So you get:

• vir innocens = an innocent man
• femina innocens = an innocent woman
• crimen innocens would also use innocens in the nominative singular

Even though femina is feminine, the adjective does not have to look feminine in the way a first/second-declension adjective would.

Because of the role of est.

• femina innocens by itself could mean an innocent woman
• femina innocens est means the woman is innocent

Here innocens is a predicate adjective, describing femina through the verb est.

So the pattern is:

• noun + adjective + est
• femina innocens est = the woman is innocent

Because crimen is a neuter noun.

• crimen = nominative singular neuter
• falsum = nominative singular neuter

The adjective must agree with the noun it modifies in:

• gender
• number
• case

So:

• crimen falsum = false charge / false accusation / false crime

It is not falsa, because that would be feminine, and crimen is not feminine.

Because this phrase is the predicate nominative after est.

In Latin, with forms of to be, both the subject and the thing identified with it are usually in the nominative:

• crimen falsum = nominative
• maxima iniuria = nominative
• est links them

So the structure is:

• crimen falsum = subject
• maxima iniuria = predicate nominative
• est = is

If it were maximam iniuriam, that would be accusative, which would not fit this construction.

Maxima is the superlative form of magnus (great), so it means greatest or sometimes more loosely very great.

It agrees with iniuria:

• iniuria = feminine singular nominative
• maxima = feminine singular nominative

So maxima iniuria means:

• the greatest injustice
• or in a less literal but natural translation, a very great injustice

Both crimen falsum and maxima iniuria are nominative, so in principle either side of est could be taken as subject-complement structure. But Latin usually expects you to decide from meaning and context.

Here the more natural reading is:

• crimen falsum = the thing being discussed
• maxima iniuria = what it is being called

So:

• A false charge is the greatest injustice

In other words, crimen falsum is treated as the subject, and maxima iniuria as the predicate nominative.

Because Latin has no articles.

That means Latin does not have separate words for:

• the
• a
• an

So femina can mean:

• a woman
• the woman

And crimen falsum can mean:

• a false charge
• the false charge

You decide which is best from the context and the intended meaning.

Latin word order is much more flexible than English word order because the endings show grammatical relationships.

A very literal rearrangement into a more English-like order would be:

• Si femina est innocens, crimen falsum est maxima iniuria.

But Latin can say:

• Si femina innocens est, crimen falsum maxima iniuria est.

This sounds natural in Latin. The adjectives are placed close to their nouns:

• femina innocens
• crimen falsum
• maxima iniuria

And est comes at the end of each clause, which is also very common in Latin prose.

Here is the breakdown:

• si — conjunction, if
• femina — nominative singular feminine
• innocens — nominative singular, agreeing with femina

• est — 3rd person singular present of esse

• crimen — nominative singular neuter
• falsum — nominative singular neuter, agreeing with crimen
• maxima — nominative singular feminine, agreeing with iniuria
• iniuria — nominative singular feminine
• est — 3rd person singular present of esse

So the sentence is built mostly out of nominatives, because both clauses use to be.

Yes. That is an important vocabulary point.

Although crimen often gets introduced as crime, it can also mean:

• charge
• accusation
• allegation

In a sentence like this, that wider meaning often makes better sense. So crimen falsum can naturally be understood as:

• a false accusation
• a false charge

That is why the sentence can express the idea that falsely accusing an innocent woman is a very serious injustice.

It is a simple real condition.

Latin commonly uses:

• si + indicative
• indicative in the main clause

That is exactly what we have here:

• si femina innocens est
• crimen falsum maxima iniuria est

So the sentence presents the condition as a real possibility or a straightforward statement, not as something hypothetical, unlikely, or contrary to fact.