rectilinear regression vs linear regression

rectilinear regression and linear regression both are nouns.

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

As nouns, rectilinear regression and linear regression are synonyms defined as:

rectilinear regression and linear regression: the relation between variables when the regression equation is linear: e.g., y = ax + b

rectilinear regression (noun)	linear regression (noun)
the relation between variables when the regression equation is linear: e.g., y = ax + b	the relation between variables when the regression equation is linear: e.g., y = ax + b