Sign (Positive and Negative) — Definition, Formula & Examples
Sign is the part of a number that tells you whether it is positive (above zero) or negative (below zero). A positive sign (+) means the number is greater than zero, and a negative sign (−) means it is less than zero.
The sign of a real number indicates its position relative to zero on the number line. A number is positive if it is greater than zero, negative if it is less than zero, and zero itself has no sign (or is sometimes considered to have its own sign).
How It Works
Every number other than zero has a sign. Positive numbers like 5 or 12 sit to the right of zero on a number line. Negative numbers like −3 or −7 sit to the left. You usually do not write the + sign for positive numbers — the number 5 and +5 mean the same thing. Negative numbers always need the − sign written in front of them.
Worked Example
Problem: Identify the sign of each number: 8, −4, 0, −15, +3.
Step 1: 8 is greater than zero, so its sign is positive.
Step 2: −4 is less than zero, so its sign is negative.
Step 3: 0 is neither positive nor negative — it has no sign. −15 is negative, and +3 is positive.
Answer: 8: positive, −4: negative, 0: neither, −15: negative, +3: positive.
Why It Matters
Understanding sign is essential for working with temperature (above or below freezing), money (earning vs. owing), and elevation (above or below sea level). It is the foundation for learning how to add, subtract, multiply, and divide integers.
Common Mistakes
Mistake: Thinking that zero is positive.
Correction: Zero is neither positive nor negative. It is the boundary point between positive and negative numbers on the number line.