Příčinou je únik vody.

Příčinou is the instrumental singular form of příčina.

In Czech, after být (to be), the noun that describes what something is is often put in the instrumental, especially in sentences like this one. So Příčinou je... is a very natural pattern meaning The cause is...

Using příčina here would sound much less natural. The instrumental also helps show that příčinou is the complement, while únik vody is the thing being identified.

Because vody is in the genitive singular.

The phrase únik vody literally means leakage of water or water leak. After a noun like únik (leakage, escape), Czech usually puts the thing that is leaking in the genitive.

So:

• voda = water
• vody = of water

This is a very common Czech pattern:

• únik plynu = gas leak
• únik informací = information leak
• spotřeba energie = energy consumption

The subject is únik vody.

Even though příčinou comes first, Czech word order is much more flexible than English word order. The form únik is nominative singular, which marks it as the subject here.

So grammatically, the sentence is structured like:

• únik vody = subject
• je = is
• příčinou = complement in the instrumental

Both are possible, but they put the emphasis in different places.

Czech often places new or important information later in the sentence. In Příčinou je únik vody, the key information is únik vody, so it comes at the end.

This version feels like an answer to a question such as:

• What is the cause?

By contrast, Únik vody je příčinou would put more emphasis on příčinou and is less natural in many contexts.

Únik basically means escape, leak, or leakage, depending on context.

So it can be used for different kinds of things:

• únik vody = water leak
• únik plynu = gas leak
• únik dat = data leak
• únik vězně = a prisoner's escape

So the core idea is that something is getting out when it should not.

Czech has no articles, so there is no separate word for the or a/an.

That means Czech simply says:

• Příčinou je únik vody.

and English has to decide whether that means something like:

• The cause is a water leak
• The cause is the leakage of water
• A cause is water leakage

The exact choice depends on context. Czech leaves that unstated.

A rough pronunciation guide is:

PŘÍ-či-nou ye Ú-nik VO-dy

A few useful points:

• ř is the famous Czech sound with no exact English equivalent; it is something like a rolled r mixed with a zh sound.
• č sounds like ch in church.
• je sounds like ye.
• ú and í are long vowels.
• Stress in Czech usually falls on the first syllable of each word:
  • PŘÍčinou
  • je
  • Únik
  • VOdy

So even if ř is difficult, getting the first-syllable stress right will already make your pronunciation sound much more Czech.