Of or related to a line or outlines; composed or comprising outlines: as, linear drawing; linear perspective.
concerning length only; specifically, in math and physics, concerning dimension in one dimension only, or a sum of such dimensions; concerning just right outlines; unidimensional; for the first degree: because, linear numbers; linear measure.
In bot., zoöl, and anatomy, like a line or bond; thin; really thin and elongate: as, a linear leaf.
In prosody, consisting in or regarding a succession of single verses all the same rhythm and size; stichic: as, linear structure; “Paradise missing” is linear in structure.
How would you define linear?