Princeps bona patriae magno auxilio est.

Princeps is nominative singular, so it is the subject of est.

It is a third-declension noun, from princeps, principis. Depending on context, it can mean leader, chief, ruler, or sometimes emperor.

So the basic frame is:

• princeps = the subject
• est = is

This is a very common Latin idiom:

• alicui auxilio esse = to be a help to someone
• more literally, to be for help to someone

So magno auxilio est means is a great help or is of great assistance.

Grammatically:

• auxilio is dative singular
• magno is also dative singular, agreeing with auxilio

This use is often called the predicate dative. If another dative is also present, teachers may call it part of the double dative construction.

The form patriae can be either:

• dative singular = to/for the fatherland
• genitive singular = of the fatherland

Those two forms look the same in the first declension, so you have to decide from context.

In a sentence with auxilio est, a learner will usually first think of dative singular: to the fatherland. That fits the normal pattern someone is a help to someone.

This is the hardest word in the sentence as written.

By form, bona could be:

• neuter plural nominative/accusative of bonus
• feminine ablative singular of bonus

That is why it feels awkward: neither possibility fits very neatly into the sentence in an obvious way.

So if you stopped and thought something seems off here, that is a very reasonable reaction. Many learners would suspect that:

• there is missing context, or
• the text may contain a typo

For example, if bonus were supposed to agree with patriae, you would expect bonae, not bona.

So the short answer is: bona is the form that deserves the most caution here.

Latin relies much more on case endings than on word order.

In English, word order usually tells you who is doing what. In Latin, endings do much of that work, so authors can move words around more freely for:

• emphasis
• style
• rhythm

That is why a Latin sentence often does not appear in the same order as its English translation.

Because Latin very often places the verb late in the sentence, especially in simple statements.

That does not mean it must always go there, but verb-final order is extremely common. A learner should get used to reading a Latin sentence by watching the endings first and not expecting English order.

Latin has no articles equivalent to English the or a/an.

So princeps could mean:

• the leader
• a leader

You decide from context and from the meaning of the whole sentence. This is completely normal in Latin.