linear vs rectilineal

linear and rectilineal both are adjectives.

Word	Noun	Adjective	Verb	Adverb
linear	No	Yes	No	No
rectilineal	No	Yes	No	No

linear (adjective)	rectilineal (adjective)
of or in or along or relating to a line; involving or having a single dimension	characterized by a straight line or lines
designating or involving an equation whose terms are of the first degree
of a circuit or device having an output that is proportional to the input
measured lengthwise
(of a leaf shape) long and narrow