der  Hohlraum

C1

Estimated CEFR level.

/ˈhoːlʁaʊm/

🔍 What exactly is a Hohlraum?

A Hohlraum (noun, masculine: der Hohlraum) refers to an empty, enclosed space within a solid body or structure. It's essentially a 'hole' or 'void' surrounded by material.

Imagine, for example:

• The space inside a cavity wall (in construction).
• A bubble or air pocket in a cast piece (in engineering).
• A natural cave within a rock (in geology).

The word is composed of hohl (hollow) and Raum (space, room, area). It only takes one article: der Hohlraum.

Article rules for der, die, and das

📚 Grammar: Der Hohlraum in Detail

The noun Hohlraum is masculine. Here is its declension:

Singular

Plural

Example Sentences

1. Im alten Baumstamm entdeckten die Kinder einen großen Hohlraum.
   (In the old tree trunk, the children discovered a large cavity.)
2. Die Bauarbeiter füllten den Hohlraum in der Wand mit Dämmmaterial.
   (The construction workers filled the cavity in the wall with insulation material.)
3. Durch die Röntgenaufnahme wurde ein Hohlraum im Knochen sichtbar.
   (A cavity in the bone became visible through the X-ray.)
4. Die Physik beschäftigt sich auch mit Resonatoren, die spezielle Hohlräume nutzen.
   (Physics also deals with resonators that use special cavities.)

🧮 When to use Hohlraum?

The term Hohlraum is used in various contexts:

• Construction & Architecture: Describing spaces within walls, ceilings, or floors, often for insulation or installations (e.g., Hohlraumdämmung - cavity insulation, Hohlraumboden - raised floor/access floor).
• Engineering & Material Science: Denoting air pockets, casting defects, or specific technical components like resonators (e.g., Hohlraumresonator - cavity resonator in microwave technology). Also, Hohlraumversiegelung (cavity sealing) in cars is a common example to prevent corrosion.
• Medicine: Describing anatomical or pathological cavities in the body (e.g., sinuses, cysts).
• Geology: Referring to natural caves or underground voids.
• General: Any empty space within an otherwise solid object.

Distinction: While a Lücke (gap) often denotes a missing part in a series or surface, and Leere (emptiness) refers to a general state of absence, a Hohlraum specifically means an enclosed empty space inside something.

🧠 Mnemonics to Remember

Article: Think of derelict buildings full of hollow rooms (Hohlräume). It's masculine, der.

Meaning: Hohl sounds like 'hollow', and Raum means 'room' or 'space'. So, a Hohlraum is a hollow space.

🔄 Similar and Opposite Words

Caution: Do not confuse with Hohlweg (a sunken lane or hollow way).

😄 A Little Joke

German: Warum hat der Schweizer Käse so viele Löcher?

Damit mehr Käse in den Hohlraum passt!

English Translation: Why does Swiss cheese have so many holes?

So that more cheese fits into the cavity! (Okay, the joke works better the other way around, suggesting the holes make less cheese, but it includes the word! 😉)

📝 Poem about the Hohlraum

German:
Im Innern tief, verborgen, still,
Ein Raum, der nichts als Leere will.
Von fester Wand ringsum umhegt,
Hat Stille sich hineingelegt.
Der Hohlraum, oft ein ungenutzter Ort,
Trägt doch Geheimnisse fort.

English Translation:
Deep inside, hidden, still,
A space that wants nothing but emptiness.
By solid wall enclosed all around,
Silence has laid itself down within.
The cavity, often an unused place,
Yet carries secrets forth.

❓ Riddle Time

German:
Ich bin ein Raum, doch ohne Tür,
Bin leer im Kern, was bin ich nur?
Man findet mich in Wand und Stein,
Manchmal bin ich winzig klein,
manchmal groß und tief im Bauch,
im Käse find' man mich auch.

Was bin ich?

English Translation:
I am a space, but have no door,
I'm empty at the core, what am I?
You find me in walls and stone,
Sometimes I'm tiny, barely known,
Sometimes large and deep inside,
In cheese, I also hide.

What am I?

Solution: Der Hohlraum (The cavity/void)

💡 Trivia and Word Formation

Word Formation: The word Hohlraum is a compound noun, formed from:

• hohl (adjective): hollow, empty inside
• der Raum (noun, masculine): space, room, area, volume

Technical Relevance: The term is very common in technical fields. Examples:

• Hohlraumversiegelung: A process to protect cavities in car bodies from corrosion (cavity sealing).
• Hohlraumresonator: A component in high-frequency technology that stores or amplifies electromagnetic waves in a cavity (e.g., in the magnetron of a microwave oven). Also known as a cavity resonator.
• Hohlraumboden: A type of flooring system with a void underneath for cables and pipes (raised floor or access floor).