SECAI Core · phase 5 of 15 · noun

Prompt compression

The reduction of the complexity of a prompt while preserving its meaning and required information in order to reduce cost in a token-limited environment

The Explain card

Plain English
Prompt compression reduces the size and complexity of a prompt while keeping its meaning and required information, so it costs fewer tokens and fits within context limits.
Example
A retrieval pipeline trims retrieved documents to the most relevant sentences and shortens a long system prompt before sending everything to the model. The request drops from thousands of tokens to a few hundred with the same answer quality.
Why it matters
Compression changes what the model sees. If a safety instruction or a "do not reveal" clause is trimmed as redundant, the guardrail disappears. Defenders test compressed prompts as carefully as the originals.
Hook
Compression squeezes the prompt; make sure the rules are not what gets squeezed out.

Word knowledge

How the word is built, where it came from, and what it sits beside in memory.

In a sentence

After the vector store returns the top-k passages, prompt compression is applied to those passages before they are concatenated with the system prompt.

Why these words
  • prompt Latin promptus, brought forth, from promere, to bring forth names the text the phrase acts on, the instruction block handed to the model
  • compression Latin compressio, a pressing together, from comprimere, to press together supplies the head noun, the packing operation borrowed from data and file compression
Where it came from
Origin
English compound on the data-compression pattern, from Latin promptus (brought forth, from promere) and Latin compressio (a pressing together, from comprimere)
Entered the language
c. 2023
What changed
Prompt had meant ready since the 1400s, then a theater cue that feeds a forgotten line, then the mark on a screen that waits for a command. Compression had meant a physical squeeze since the late 1300s, then the packing of files into fewer bits. Papers in the early 2020s joined the two on the data-compression pattern, and the phrase became the ordinary name for shrinking the text a model is given.
How it is spelled
Pattern
Latin -pt- stays a cluster, never simplified to -t-
Pattern
Latin com- stays com- before p, never reduced to co-
Pattern
-ssion of Latin -ssio names the act, as in compression, impression, depression
Breaks the pattern
the noun phrase stays two words; the hyphen appears only when it modifies another noun
Breaks the pattern
prompt is noun and verb with no spelling change
Breaks the pattern
compression keeps the double s of press plus the Latin -ion, so compress and compression do not share a letter count

Spelled like

  • attempt
  • exempt
  • impression
  • depression
Broken into chunks
  • pro
    • produce
    • promote
    • propose
  • mpt
    • attempt
    • exempt
    • contempt
  • com
    • combine
    • compose
    • compile
  • press
    • pressure
    • impress
    • depress
  • ssion
    • impression
    • depression
    • suppression
What it sits beside

Same subject

Same shape

  • data compression
  • image compression
  • file compression

Prompt compounds

Compression compounds

  • data compression
  • image compression
  • file compression

Retrieval pipeline neighbors

Where it sits in the deck

Phase 5: Interacting with Models: Prompting, APIs, and Retrieval

With a working model and clean data, learn the interaction layer — how users and systems communicate instructions and retrieve grounded answers.

Neighbours in this phase