Si omnes honesti et fideles sunt, fama bona manet et salus omnium facilius servatur.

It has two parts:

• Si omnes honesti et fideles sunt = the if-clause
• fama bona manet et salus omnium facilius servatur = the main clause

So this is a straightforward conditional sentence: if X is true, Y follows.

Because the subject is omnes, which is plural.

• est = is (singular)
• sunt = are (plural)

Since omnes means all or all people, the verb must also be plural: omnes ... sunt.

Omnes is nominative plural, and here it is being used almost like a noun by itself: all people, everyone, or simply all.

Latin often does this with words like omnes:

• omnes veniunt = everyone comes / all come

So in this sentence, you can understand an implied noun such as homines:

• omnes honesti et fideles sunt
  = all people are honorable and faithful

They are predicate adjectives describing omnes, so they must agree with it in number and case.

• omnes = nominative plural
• honesti = nominative plural
• fideles = nominative plural

They go with sunt:

• omnes honesti et fideles sunt
  = all are honorable and faithful

This is like English they are honest, where honest describes the subject after the verb are.

Because honestus, -a, -um is a 1st/2nd-declension adjective.

Its masculine nominative plural form is honesti.

So if omnes is understood as referring to people in a general or mixed group, Latin normally uses the masculine plural as the default:

• honestus → honesti

Because fidelis, fidele belongs to a different adjective pattern.

It is a 3rd-declension adjective, so its nominative plural form is:

• fideles for masculine/feminine plural

So the difference is just due to different declensions:

• honestus → honesti
• fidelis → fideles

Both still agree with omnes.

This is a simple, real condition.

• si ... sunt = if ... are
• manet / servatur = remains / is preserved

Latin uses the present indicative in both parts for a condition that is presented as real, general, or straightforward.

It is not a hypothetical or contrary-to-fact condition. So you do not get subjunctives like sint here.

Because Latin often leaves it out.

English can say:

• If everyone is honest and faithful, then good reputation remains...

But Latin very often just says:

• Si ... , fama bona manet ...

The idea of then is understood automatically from the si clause.

Latin word order is more flexible than English word order.

Both fama bona and bona fama can mean good reputation. In this sentence, fama bona is simply the chosen order.

Important point: the meaning comes from the endings, not just the position.

• fama = nominative singular
• bona = nominative singular feminine, agreeing with fama

So they belong together no matter which comes first.

Because its subject is fama bona, which is singular.

• fama bona = good reputation
• manet = remains

Even though omnes earlier is plural, that plural belongs to the if-clause. In the main clause, the subject of manet is a different word: fama.

Omnium is genitive plural.

It depends on salus and means:

• salus omnium = the safety of all / the welfare of all

So omnium answers the question whose safety? → the safety of all.

That is why it is genitive.

Because the sentence needs the meaning of all, not for all or by/with all.

• omnium = genitive plural = of all
• omnibus = dative or ablative plural = to/for all or by/with/from all

Here the phrase is possessive or dependent on salus:

• salus omnium = the safety of all

So omnium is the correct form.

Salus can mean several related things, depending on context:

• safety
• well-being
• welfare
• sometimes health
• sometimes even salvation

In this sentence, the most natural sense is something like safety or welfare, especially because it is followed by servatur (is preserved/protected).

Facilius is a comparative adverb meaning more easily.

It modifies the verb servatur:

• servatur = is preserved
• facilius servatur = is preserved more easily

It is not describing a noun; it is describing how the action happens.

Here it is an adverb.

A useful comparison:

• facilis = easy (adjective)
• facile = easily (adverb)
• facilius = more easily (comparative adverb)

So in this sentence, facilius tells us the manner of servatur.

Servatur is present passive, third person singular:

• servat = he/she/it preserves
• servatur = he/she/it is preserved

Its subject is salus:

• salus ... servatur = the safety ... is preserved

Latin commonly uses the passive when the focus is on the thing being protected or preserved rather than on the person doing the protecting.

They are two coordinated verbs in the main clause, joined by et:

• fama bona manet
• et salus omnium facilius servatur

So the sentence says that, if the condition is met, two results follow:

1. good reputation remains
2. the safety of all is more easily preserved

Each verb has its own subject:

• manet → subject: fama bona
• servatur → subject: salus omnium

Yes, you can understand something like homines (people) if you want.

So:

• omnes honesti et fideles sunt

can be understood as:

• omnes homines honesti et fideles sunt

But Latin does not need to state homines explicitly. Omnes by itself is enough.