1
general::
a small piece
fragment
a small piece that has broken off something, especially something hard:
• The window shattered, covering them with fragments of glass. • They found fragments of bone.
crumb
a very small piece of bread, cake etc:
• There were just a few crumbs left on the plate.
speck
a piece of something such as dirt or dust which is so small you almost cannot see it:
• She brushed the specks of dust from the table.
drop
a very small amount of a liquid:
• There were drops of blood on the floor. • I felt a drop of rain.
Longman-Thesaurus