Drenážní vrstva je nad odtokovým otvorem.

It breaks down like this:

• Drenážní vrstva = the subject
• je = the verb is
• nad odtokovým otvorem = a prepositional phrase showing location: above the drain opening / outlet hole

So the basic pattern is:

[subject] + [is] + [location]

Czech normally does not use articles like English the and a/an.

So Drenážní vrstva je nad odtokovým otvorem can mean something like:

• The drainage layer is above the drain hole
• or, depending on context, A drainage layer is above a drain hole

Czech usually leaves definiteness to context, word order, or the wider situation.

Because drenážní is a soft adjective ending in -ní, and in the nominative singular it has the same form for masculine, feminine, and neuter nouns.

So:

• drenážní vrstva = feminine
• drenážní systém = masculine
• drenážní potrubí = neuter

All still use drenážní in that form.

This is different from adjectives like dobrý / dobrá / dobré, where the ending changes visibly by gender.

• vrstva is feminine
• otvor is masculine inanimate

This matters because in Czech:

• adjectives must agree with the noun they describe
• noun endings change by case
• adjective endings also change by case, number, and gender

So:

• drenážní vrstva: adjective agrees with feminine vrstva
• odtokovým otvorem: adjective agrees with masculine inanimate otvor, and both are in the same case

Because the preposition nad can take two different cases:

• instrumental for location: above
• accusative for motion toward a position above

Here the meaning is static location, so Czech uses the instrumental:

• nad odtokovým otvorem = above the drain opening

Compare:

• Obraz visí nad stolem. = The picture is hanging above the table.
  → location, so instrumental
• Pověsím obraz nad stůl. = I will hang the picture above the table.
  → movement to that position, so accusative

So in your sentence, nothing is moving; it is simply located there.

Those endings show the instrumental singular.

1. otvorem

The base noun is otvor.
In the instrumental singular, a masculine inanimate noun like this becomes:

• otvor → otvorem

2. odtokovým

The adjective odtokový must agree with otvorem, so it also goes into instrumental singular masculine/neuter:

• odtokový → odtokovým

So the whole phrase is:

• nad odtokovým otvorem

with both adjective and noun in the instrumental after nad.

Literally, it is something like:

• odtokový = related to drainage / outflow / discharge
• otvor = opening / hole

So odtokový otvor is literally drainage opening, outlet opening, or drain hole, depending on context.

In technical language, Czech often uses these compact adjective + noun combinations where English might prefer a noun + noun structure, such as drain hole.

No, Czech word order is fairly flexible because grammatical roles are often shown by case endings, not only by position.

Your sentence is a neutral, straightforward version:

• Drenážní vrstva je nad odtokovým otvorem.

But you could also say:

• Nad odtokovým otvorem je drenážní vrstva.

That version puts more focus on the location first, somewhat like Above the drain opening is the drainage layer.

So the word order can change, but the choice affects emphasis and information focus.

In standard Czech, the present-tense form of být (to be) is usually kept in normal sentences like this.

So:

• Drenážní vrstva je nad odtokovým otvorem. = normal, complete sentence

Leaving out je would usually sound unnatural here, or like a note, label, or very compressed style.

Unlike some other Slavic languages, Czech generally does not omit the present-tense is in ordinary sentences.

Yes. Like English over or above, Czech nad can also be used in non-physical meanings in some contexts, for example in more abstract expressions.

But in this sentence it is clearly physical location:

• the drainage layer is above the drain opening

So here you should understand nad very literally.

A rough guide:

• drenážní ≈ dre-NAAZH-nee

  • á is long
  • í is long

• vrstva ≈ VRST-va
  This is tricky for English speakers because Czech allows consonant-heavy clusters. The r can act almost like the center of the syllable.

• odtokovým ≈ OT-to-ko-veem

  • stress is on the first syllable
  • ý is long

• otvorem ≈ OT-vo-rem

One useful general rule: Czech stress is usually on the first syllable of the word.