(n.) a component; formerly, a period of 1/15th of an hour
A quick vocabulary lesson. One of this week’s most curious facts over on HH was that 1/15th of an hour—a period of precisely 4 minutes—is called a part:
And a while back, we found out that a moment was once precisely defined as 1/40th of an hour, or precisely 90 seconds:
But when it comes to divisions of time nobody uses any more, these two are just the tip of a temporal iceberg.
1/4 of an hour (as well as being called a quarter of an hour, of course) was once known as a punct, or point. And two 15-minute puncts made a semihore, or half-hour.
A scruple was once variously used to describe 1/60th of a day (precisely 24 minutes), or 1/18th of a minute (precisely 3 1/3 seconds). And smallest of all was the atom, which by mediaeval reckoning corresponded to 1/376th of a minute—meaning that there were over 22,000 atoms in an hour.
There were no mechanisms accurate enough to correctly time an atom back in the mediaeval period, of course, so the term was typically only used theoretically. For that reason, appropriately enough, this smallest of the smallest subdivisions of time was given a name essentially meaning “individable.”