Princeps bonum commune ac salutem civitatis spectare debet.

The subject is princeps.

It is in the nominative singular, and it means leader, chief, ruler, or statesman, depending on context. Since Latin often leaves out articles, princeps can mean the leader or a leader.

So the basic structure is:

• princeps = the subject
• debet = the main verb
• spectare = the action that debet governs
• bonum commune ac salutem civitatis = what the leader ought to consider

Because it depends on debet.

Latin often uses debeo + infinitive to mean:

• ought to
• should
• must

So:

• debet = he/she/it ought
• spectare = to look at / consider / have regard for

Together, spectare debet means ought to consider or must have regard for.

This is very similar to English ought to consider.

Debet is the 3rd person singular present active indicative of debeo, debere.

In this sentence it means something like:

• ought to
• should
• must

The exact English choice depends on tone:

• ought to is often a very good match
• should can sound a little softer
• must can sound stronger

So Princeps ... spectare debet means The leader ought to consider... or A ruler must look to...

Literally, spectare does mean to look at, watch, or observe. But in this sentence it has a more extended sense.

Here it means something like:

• to look to
• to consider
• to pay attention to
• to have regard for
• to keep in view

So this is not mainly about physically looking at something. It is about directing one’s concern or attention toward something.

They are the direct objects of spectare.

Even though spectare is an infinitive, it can still take its own objects. The leader ought to consider what?

• bonum commune = the common good
• salutem civitatis = the safety/welfare of the state

That is why both are in the accusative:

• bonum
• commune
• salutem

Because the phrase is neuter singular accusative.

Here bonum means good, and commune means common. They agree with each other in:

• gender: neuter
• number: singular
• case: accusative

So:

• bonum = good / the good
• commune = common

Together: bonum commune = the common good

A learner may expect bonus or communis, but those would not match this form. Since the phrase is functioning as an object and is neuter singular, the correct form is bonum commune.

You can think of it as an adjective being used substantively, or simply as a noun-like word meaning good.

In Latin, adjectives are often used as nouns when the meaning is clear. So bonum can mean:

• a good thing
• the good
• the good interest

In the fixed phrase bonum commune, the whole expression means the common good.

For a learner, the most useful thing is simply to recognize bonum commune as a standard political and ethical expression.

Because commune is the neuter singular accusative form of communis, commune.

This adjective has:

• masculine/feminine accusative singular: communem
• neuter nominative/accusative singular: commune

Since bonum is neuter singular accusative, the adjective agreeing with it must also be neuter singular accusative:

• bonum commune

Civitatis is genitive singular of civitas.

It depends on salutem and means:

• of the state
• of the community
• of the body politic

So:

• salutem civitatis = the safety of the state / the welfare of the commonwealth

This is a very common Latin pattern: a noun followed by a genitive that specifies whose or what kind of thing it is.

Because the phrase does not mean the safety and the state as two separate objects.

Instead, civitatis modifies salutem:

• salutem = safety, welfare
• civitatis = of the state

So the meaning is the safety of the state, not the safety and the state.

If it were civitatem, that would be another accusative object, and the meaning would be quite different.

Not exactly. Although English words like city are historically related, Latin civitas usually means something broader, such as:

• state
• commonwealth
• body of citizens
• political community

So in this sentence, civitatis is better understood as of the state or of the community, not just of the city in a physical sense.

Ac means and.

It is a variant of atque, and both often mean essentially the same thing as et. In many sentences, you can translate all of them simply as and.

So here:

• bonum commune ac salutem civitatis = the common good and the safety of the state

A useful note: ac is commonly used before consonants, while atque is the fuller form.

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

English depends heavily on position:

• The ruler ought to consider the common good

Latin can move words around more freely because case endings tell you what each word is doing.

This sentence places:

• Princeps first, giving prominence to the ruler
• debet at the end, which is a very natural and common Latin placement for the main finite verb

So the order is stylistic and idiomatic, not random.

Because Latin has no definite article like English the.

So princeps can mean:

• a leader
• the leader

and bonum commune can mean:

• common good
• the common good

You decide from context which English article sounds best.

It is singular.

Even though the ending may not look familiar at first, princeps is a third-declension noun, and its nominative singular is princeps.

So the sentence refers to one leader or ruler, not several.

Yes. A very literal version might be:

• The leader ought to look toward the common good and the safety of the state.

But more idiomatic English might be:

• A ruler should keep the common good and the welfare of the state in view.
• A leader ought to consider the common good and the safety of the state.
• A ruler must have regard for the common good and the welfare of the state.

These all capture the idea well, even if they are not word-for-word translations.