Definition
Fraction notation
Fraction notation writes a numerator over a nonzero denominator, joined by a fraction bar.
What it means
The bottom number tells the equal-part size, and the top number tells how many of those parts are counted. In 3/5, a whole is split into 5 equal parts and 3 are counted. The same notation also names 3 divided by 5, even when no picture of a whole is used.
Remember it
Top counts; bottom names the equal-part size; the bar means divide.
Example
A ribbon is cut into 5 equal lengths and Lina uses 3. Write 3/5: 3 is the numerator, 5 is the denominator, and the fraction bar means 3 ÷ 5.
Watch for
The denominator cannot be zero because division by zero is undefined. A ratio written 3:5 uses ratio notation, not standard fraction notation.
Common mix-up
Swapping 3/5 to 5/3 changes the number; numerator and denominator have different jobs.
Exact meaning
Fraction notation writes one number, the numerator, above another nonzero number, the denominator, with a fraction bar between them; inline, the same structure can be written a/b. The bar means division, so a/b names the number a ÷ b.