scintilla

scintilla \sin-TIL-uh\, noun:

A tiny or scarcely detectable amount; the slightest particle; a trace; a spark.

In victory, they must hold on to at least a scintilla of humility, lest they get too cocky -- and ripe for a takedown.
-- Bill Breen, "We are literally trying to stop time", Fast Company, May 2000

I bear her not one scintilla of ill will, he said.
-- Sarah Lyall, "That Harriman Book", New York Times, May 4, 1994

There was never a scintilla of doubt, or a hint of equivocation, in Michael about his commitment to the party.
-- "Ferris's decency and sense of fun recalled", Irish Times, March 23, 2000

Scintilla is from Latin scintilla, "a spark, a glimmer, a faint trace." Also from scintilla is the verb scintillate, "to sparkle."