1.Definition: (of a leaf shape) long and narrow

Related Adjective(s):elongate

2.Definition: designating or involving an equation whose terms are of the first degree

Related Adjective(s):additive

3.Definition: measured lengthwise

Related Adjective(s):running

4.Definition: of a circuit or device having an output that is proportional to the input

"Linear amplifier"

Related Adjective(s):analog, analogue

5.Definition: of or in or along or relating to a line; involving or having a single dimension

"A linear measurement"