What is a line number, not a number line, but a line number?

Question

What is a line number, not a number line, but a line number?

Answer 1

Many documents have line numbers.  Legal briefs, computer programs, scientific treatises, and religious writings are examples that come to mind.

Answer 2

A line number is simply a reference to a line in a page of text or in a computer program.

Here is a very simple program in Basic (an early programming language) that keeps adding 1 to X until X=42. It uses line numbers to tell the computer where to look for the next set of instructions

10 IF X = 42 GOTO 40

20 X = X + 1

30 GOTO 10

40 PRINT "X is finally 42!"

Hope this is helpful!