Answer:

neper

Answer	Crossword Clue
NEPER	Physics ratio unit
NEPER	Mathematician Napier a.k.a. ...
NEPER	Logarithm word

NEPER	Physics ratio
NEPER	Logarithmic unit
NEPER	Father of logarithms
NEPER	Logarithm unit

Crossword

a puzzle consisting of a grid of squares and blanks into which words crossing vertically and horizontally are written according to clues.