Arrha cautionem firmam reddit.

The subject is arrha.

You can tell because:

• arrha is in the nominative singular
• reddit is third person singular
• cautionem and firmam are accusative forms, so they are not the subject

So the basic structure is:

• arrha = subject
• cautionem = direct object
• firmam = describes the object after the action
• reddit = verb

Yes, arrha is singular.

It is a first-declension feminine noun:

• nominative singular: arrha
• genitive singular: arrhae

So even though -a may look unusual to an English speaker, here it is just a normal first-declension singular nominative ending.

You may also sometimes see the spelling arra in Latin.

Because it is the direct object of reddit.

The verb is acting on cautionem, so Latin puts it in the accusative case.

The dictionary form is:

• cautio, cautionis = security, guarantee, bond, precaution

Its accusative singular is cautionem.

So:

• cautio = nominative
• cautionem = accusative

Because firmam goes with cautionem, not with arrha.

It agrees with cautionem in:

• gender: feminine
• number: singular
• case: accusative

This is a very common pattern after verbs like reddere in the sense of render/make:

• verb + object + object complement

So cautionem firmam reddit means something like:

• renders the guarantee firm
• makes the security firm

Here firmam is not a separate noun or a subject adjective; it is an adjective describing what the object becomes.

That is a very common question.

Reddere can indeed mean give back, but it also has a broader sense: render, cause to be, make.

So in this sentence, reddit does not mean literal returning. It means:

• renders
• makes
• causes to be

That is why cautionem firmam reddit means makes the guarantee firm rather than gives back the guarantee firm.

Not exactly.

This is a helpful false-friend warning.

In English, caution often means:

• carefulness
• a warning

But Latin cautio often means:

• security
• guarantee
• bond
• legal assurance

So in this sentence, cautionem is not really a warning. It is more like a guarantee or security.

Because Latin has no articles.

Latin does not have separate words for:

• a / an
• the

So whether you translate a noun as a guarantee or the guarantee depends on the context, not on a special article.

That is completely normal in Latin.

Yes. Latin word order is much freer than English word order because the endings show the grammatical roles.

So all of these would still make grammatical sense:

• Arrha cautionem firmam reddit
• Cautionem firmam arrha reddit
• Arrha firmam cautionem reddit

The usual reason for changing the order would be emphasis or style.

In your sentence, the order is quite natural:

• subject first
• object phrase in the middle
• verb at the end

Also, keeping firmam next to cautionem makes it clear that they belong together.

No. Latin adjectives can come either before or after the noun.

So both of these are possible:

• cautionem firmam
• firmam cautionem

They mean the same basic thing.

In your sentence, cautionem firmam is simply the chosen word order. Latin often allows this flexibility, unlike English, where adjective position is much more fixed.

They are:

• arrha, arrhae — deposit, earnest-money pledge
• cautio, cautionis — security, guarantee, bond
• firmus, firma, firmum — firm, strong, secure
• reddo, reddere, reddidi, redditum — give back, render, make

Knowing the dictionary forms helps you see why the sentence looks the way it does:

• arrha = nominative singular
• cautionem = accusative singular
• firmam = accusative singular feminine agreeing with cautionem
• reddit = present active indicative, third person singular