Scintilla

: spark, trace

Example sentence:
After the witness's frank and bruising testimony, neither my brother nor I was left with a scintilla of doubt that the defendant was guilty.

Did you know?
"Scintilla" comes directly from Latin, where it carries the meaning of "spark" — that is, a bright flash such as you might see from a burning ember. In English, however, our use of "scintilla" is restricted to the figurative sense of "spark" — a hint or trace of something that barely suggests its presence. The Latin "scintilla" is related to the verb "scintillare," which means "to sparkle" and is responsible for our verb "scintillate" ("to sparkle or gleam," literally or figuratively). In an odd twist, "scintilla" underwent a transposition of the "c" and the "t" (a linguistic phenomenon known as metathesis) to create the Vulgar Latin form "stincilla," which is believed to be an ancestor of our word "stencil."