Scintilla (noun)

1. A tiny amount or trace of something.
2. A spark or flash of light.
3. A small particle of radioactive material used in medical imaging.

Origin:

From latin scintilla, meaning a spark or a trace.

Examples:

1. There was not a scintilla of doubt in his mind.
2. The fireworks display was accompanied by a shower of scintillas.
3. The scintilla camera was used to detect the spread of cancer in the patient's body.
4. A scintilla of hope remained in her heart.
5. The nuclear reaction produced only a few scintillas of energy.