Si vas fragile est, puerum illud tangere non sinimus.

Si means if and introduces a condition.

So the sentence has two parts:

• Si vas fragile est = if the vase/vessel is fragile
• puerum illud tangere non sinimus = we do not allow the boy to touch that/it

This is a straightforward present-time condition: if X is true, we do Y.

This is a very common Latin pattern:

• vas = the vase / vessel
• fragile = fragile
• est = is

So vas fragile est literally means the vase is fragile.

Here fragile is a predicate adjective: it describes vas after a form of to be.

Because vas is neuter singular, and the adjective has to match it.

The adjective fragilis, fragile has different forms:

• masculine/feminine nominative singular: fragilis
• neuter nominative singular: fragile

Since vas is neuter, Latin uses fragile.

Here vas is nominative singular, because it is the subject of est.

A detail that often surprises learners: vas is one of those nouns whose nominative singular and accusative singular look the same. So the form vas can be either nominative or accusative depending on its job in the sentence.

In this sentence, it is nominative because it is the thing that is fragile.

Because sinere often uses an accusative + infinitive construction.

So:

• puerum = the boy in the accusative
• tangere = to touch

Together, puerum tangere sinimus means we allow the boy to touch.

In English, the boy looks like the subject of to touch, but in Latin, with verbs like sinere, that person is commonly put in the accusative.

Because after sinimus it expresses the action that is being allowed or not allowed.

• sinimus = we allow
• tangere = to touch

So the structure is:

• we allow
• someone
• to do something

Latin expresses that to do something with the infinitive, here tangere.

Also, Latin does not need a separate word for English to before the verb; the infinitive form itself already includes that idea.

Because they are doing different jobs.

• puerum is the person being allowed or not allowed to act
• illud is the object of tangere

So the structure is:

• puerum = the boy
• illud tangere = to touch that

In other words, one accusative is tied to sinimus, and the other is the direct object of the infinitive tangere.

This kind of double-accusative-looking sequence is very normal in Latin with verbs like sinere.

Illud is a neuter accusative singular form of ille, illa, illud.

Here it is most naturally understood as that thing or that used as a pronoun. Depending on the context, it may refer back to the vas.

So illud tangere means to touch that or to touch it, with a more demonstrative sense than a plain pronoun.

Because illud does not go with puerum.

A very common beginner question is whether puerum illud could mean that boy. It cannot, because the words do not agree:

• puerum = masculine accusative singular
• illud = neuter accusative singular

If Latin wanted to say that boy, it would use illum puerum or puerum illum.

So in the sentence as written, illud must be separate from puerum and is best taken as that thing / it.

Because the main idea being negated is we do not allow.

So:

• non sinimus = we do not allow

The sentence is not primarily saying the boy touches not; it is saying we refuse permission / we do not permit the touching.

Latin often places non directly before the word it most clearly negates, and here that is the main verb sinimus.

The ending -mus tells you the subject is we.

So:

• sino = I allow
• sinimus = we allow

Because of that ending, Latin does not need a separate subject pronoun like nos unless it wants emphasis.

Yes, the word order is acceptable, and Latin word order is much freer than English word order.

The sentence could be rearranged in other ways without changing the basic meaning, because the case endings and verb forms show the grammatical relationships.

For example, Latin can move words around for emphasis. In this sentence:

• the if-clause comes first
• the main verb sinimus comes at the end, which is very common
• illud is placed before tangere, which keeps it close to the action it belongs with

So word order in Latin is guided more by emphasis and style than by rigid rules like in English.

Yes. If the intended Latin were that boy, the demonstrative should be masculine accusative singular, not illud.

You would expect:

• illum puerum or
• puerum illum

So if your meaning gloss says that boy, but the Latin text has illud, that is something to question. As written, illud is neuter and most naturally means that thing or refers back to a neuter noun such as vas.