Truhlu lze odemknout.

Because truhlu is the accusative singular form of truhla.

• truhla = nominative singular, the basic dictionary form
• truhlu = accusative singular, used here because it is the direct object of odemknout

So the pattern is:

• truhla = a/the chest, as subject
• truhlu = a/the chest, as object

This is a very common feminine noun pattern in Czech.

Lze is an impersonal verb form meaning something like:

• it is possible
• one can
• can be

It is commonly followed by an infinitive:

• lze odemknout = can be unlocked / it is possible to unlock

It is fairly neutral to formal in style. In everyday speech, Czechs often use dá se instead:

• Truhlu lze odemknout.
• Truhlu se dá odemknout.

These are very similar in meaning, but lze sounds a bit more formal or written.

Because Czech does not need a dummy subject like English it.

In English, we say:

• It is possible to unlock the chest.

But in Czech, lze already works as an impersonal expression, so no subject is needed. Czech often leaves out things that English must state explicitly.

So Truhlu lze odemknout is complete without any extra word meaning it.

Not in the strict grammatical sense.

English often translates it with a passive idea:

• The chest can be unlocked.

But Czech is not using a regular passive form here. Instead, it uses:

• object: truhlu
• impersonal modal expression: lze
• infinitive: odemknout

So it is better described as an impersonal possibility construction rather than a normal passive.

A more direct Czech passive would look different, for example with být + passive participle, but that would be less natural here.

Odemknout is the infinitive of a perfective verb meaning to unlock.

Its imperfective partner is:

• odemykat = to be unlocking / to unlock repeatedly / in process

So the pair is:

• odemykat = imperfective
• odemknout = perfective

Here the perfective verb is natural because the sentence is about whether the chest can be successfully unlocked, not about the ongoing process.

Because the sentence focuses on the result: the chest reaches the unlocked state.

With verbs of possibility, Czech often uses a perfective infinitive when talking about whether a single action can be completed:

• lze odemknout = it is possible to unlock it successfully

If you used odemykat, it would sound more like the activity or repeated action of unlocking, which is not the main point here.

So odemknout is the natural choice.

Yes. Czech word order is flexible.

You could also say:

• Lze odemknout truhlu.

That is grammatically fine. But the original order:

• Truhlu lze odemknout.

puts truhlu first, which can make it feel like the sentence is about the chest specifically.

Very roughly:

• Truhlu lze odemknout. = As for the chest, it can be unlocked.
• Lze odemknout truhlu. = It is possible to unlock the chest.

The difference is usually about focus and information structure, not basic meaning.

You negate lze:

• Truhlu nelze odemknout.

That means:

• The chest cannot be unlocked.
• It is not possible to unlock the chest.

So:

• lze = it is possible
• nelze = it is not possible

This is a very common pair in Czech.

No, not in standard Czech.

You need truhlu, not truhla, because the chest is the object of unlock.

Compare:

• Truhla je těžká. = The chest is heavy.
  Here truhla is the subject, so nominative is correct.

• Truhlu lze odemknout. = The chest can be unlocked.
  Here truhlu is the object, so accusative is correct.

This is one of the most important case distinctions to get used to in Czech.

It is common enough that learners should recognize it, especially in:

• written Czech
• instructions
• notices
• formal statements
• neutral standard language

But in casual spoken Czech, people often prefer:

• dá se

So you will often hear:

• Truhla se dá odemknout.
• Truhlu se dá odemknout.
  depending on style and structure

For a learner, it is useful to know that:

• lze = more formal/written/concise
• dá se = very common in everyday speech

Because Czech has no articles like English a and the.

So truhlu can mean:

• the chest
• a chest

The exact meaning depends on context.

In a standalone sentence like this, English often uses the chest if a specific chest is already known, but Czech does not need a separate word to show that.

Yes, it can look strange to English speakers because of the consonant cluster.

Lze is pronounced approximately like l-ze, with the l and z both clearly pronounced. The z is voiced, and the final e is a short Czech e.

The important thing is not to insert a big extra vowel between l and z. Czech allows consonant clusters that feel unusual in English.

Even if your pronunciation is not perfect at first, Czech speakers will usually understand you if you say the sounds clearly and keep the word short.