---
title: "Catch"
description: "a unit admitted by a predicate at a place, with the conditions and the words that admitted it"
section: concepts
address: /concepts/catch
contract: 0476e35e6e275db5
---

# Catch

a unit admitted by a predicate at a place, with the conditions and the words that admitted it

[figure: Catch is a fact at follows scope. The drawing shows its fields and the objects that they point at.]

| property | value |
|---|---|
| kind | fact |
| scope | follows |
| key | the hash, the unit, the place and the observation read |
| store | postgres+lake |
| family | rules_engine |



## Fields


| field | type | required | note |
|---|---|---|---|
| `predicate` | `hash` | yes |  |
| `unit` | `id` | yes |  |
| `place` | [PlaceARunsAt](/concepts/placearunsat) | yes |  |
| `observation` | `id` | yes |  |
| `conditions` | [ConditionMatch](/concepts/conditionmatch) | yes |  |
| `monitor` | `id` | no |  |



## Routes that use it
- [`/v1/read/explain_catch`](/reference/read/explain_catch) returns it