a piece; a fragment; a bit
Refers to a single small physical piece, scrap, or fragment of something.
I tore off a piece of bread and ate it.
A fragment of glass had fallen on the floor.
iota; trace; the slightest bit
Used in negative or minimal expressions to mean 'even a tiny amount', often with ～も…ない.
There wasn't a shred of truth in his story.
I have not the slightest regret.
intensive zazen meditation on a subject; knocking all into one
Compound of 一 (one) and 片 (piece, fragment). The reading いっぺん is a regular sound change from いちへん.