An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

1) A long, narrow mark, smear, band of color, or the like.
2) Mineralogy: The color that minerals leave behind when scratched against a black or white porcelain plate. It is used to identify the mineral.

From M.E. streke, from O.E. strica; akin to O.H.G. strich "line."

Xaš "streak, scratch, stria," maybe from xarâš-, xarâšidan "to scratch;" Proto-Ir. *xrāš- "to scratch" (Cheung 2007), or a variant of xatt, → line.

In → fluid mechanics, the curve defined by the positions of all particles which have passed through a given point. In laboratory experiments, streak line may be displayed by the stream of color resulting from injection of a dye into the flow.

→ streak; → line.