Ratio - Notation and Terminology

Notation and Terminology

The ratio of numbers A and B can be expressed as:

• the ratio of A to B
• A is to B
• A:B
• A fraction (rational number) that is the quotient of A divided by B

The numbers A and B are sometimes called terms with A being the antecedent and B being the consequent.

The proportion expressing the equality of the ratios A:B and C:D is written A:B=C:D or A:B::C:D. this latter form, when spoken or written in the English language, is often expressed as

A is to B as C is to D.

Again, A, B, C, D are called the terms of the proportion. A and D are called the extremes, and B and C are called the means. The equality of three or more proportions is called a continued proportion.

Ratios are sometimes used with three or more terms. The dimensions of a two by four that is ten inches long are 2:4:10.