Today, moment usually means a brief, indefinite stretch of time. In medieval timekeeping, however, it could name a specific subdivision: one moment was one fortieth of an hour. If that hour is treated like a modern sixty minute hour, the result is about 90 seconds.
The definition needs one important qualification. Medieval hours were not always equal to modern clock hours. A daylight hour could be calculated as one twelfth of the time from sunrise to sunset. Because daylight changes through the year, such an hour was longer in summer and shorter in winter. Its moments changed length too. The fraction was exact, even when the number of modern seconds was not.
This use appears in medieval systems for dividing and discussing time. It shows how a familiar word can move from a technical meaning to an everyday one. Modern speakers normally use moment loosely, and expressions such as in a moment do not promise a wait lasting exactly 90 seconds.
Compare the two uses:
- Please wait a moment while I check the record. Here, the word means a short, unspecified time.
- An hour contains forty moments. In a medieval account, the word identifies a measured fraction of the hour.
The historical sense was precise in relation to the hour, while the everyday sense is flexible. This contrast shows how word meanings can become broader and less technical over time.