regression coefficient vs rectilinear regression

regression coefficient and rectilinear regression both are nouns.

Word	Noun	Adjective	Verb	Adverb
regression coefficient	Yes	No	No	No
rectilinear regression	Yes	No	No	No

regression coefficient (noun)	rectilinear regression (noun)
when the regression line is linear (y = ax + b) the regression coefficient is the constant (a) that represents the rate of change of one variable (y) as a function of changes in the other (x); it is the slope of the regression line	the relation between variables when the regression equation is linear: e.g., y = ax + b