The approximately symbol, which looks like two parallel wavy lines, is often used to denote a value that is close enough to another number or quantity. Sometimes the sign is also referred to as double tilde. The symbol is typically placed between two numbers to show that they’re not exactly equal but are nearly so.
When to Use the Approximately Sign
There are several instances when the approximately sign is appropriate. One such example occurs when you perform an operation and cannot express the result of that operation as an exact number, or when you need to avoid representing numbers with infinite decimal expansions. In many cases, the approximate symbol allows for a value that’s sufficiently close to the real answer to be used for practical purposes. A simple example is the irrational number π, which has a decimal expansion that continues indefinitely without repeating itself.
Example of Approximate Values
In the above example, we have used the approximation symbol to show how the irrational number pi compares with its commonly used approximation of 3.14. Pi is actually roughly 3.14159265…, and rounding it to the nearest hundredth results in 3.14. Since the decimal portion of this number never ends nor repeats itself, we must use some form of numerical approximation to represent it in terms of decimals.
Comparing Symbols
Symbols like the approximately symbol are used to compare quantities, though the meanings differ. Other symbols include:
~: This is used to show that two things are similar to each other. In geometry, it’s typically used to compare figures whose angles are equal and sides are in proportion to each other.
≅: This means “congruent to,” and indicates that a figure has the same dimensions as another figure.
It’s possible to confuse these different symbols with one another; however, knowing what they mean can help you understand what they signify in your calculations.