A basis point (often denoted as bp, colloquially referred to in the plural as "bips", also known as a beep) is a unit equal to 1/100 of a percentage point or one part per ten thousand. The same unit is also (rarely) called a permyriad (literally meaning 'for (every) myriad (ten thousand)'), and in that context is written with U+2031 ‱ per ten thousand sign (HTML: ‱) which looks like a percent sign (%) with two extra zeroes at the end (like a stylized form of the four zeros in the denominator, although it originates as a natural extension of the percent (%) and permille (‰) signs).

A basis point is defined as:

It is frequently, but not exclusively, used to express differences in interest rates of less than 1% per year. For example, a difference of 0.10% is equivalent to a change of 10 basis points (e.g. a 4.67% rate increases by 10 basis points to 4.77%).

Like percentage points, basis points avoid the ambiguity between relative and absolute discussions about interest rates by dealing only with the absolute change in numeric value of a rate. For example, if a report says there has been a "1% increase" from a 10% interest rate, this could refer to an increase either from 10% to 10.1% (relative, 1% of 10%), or from 10% to 11% (absolute, 1% plus 10%). If, however, the report says there has been a "10 basis point increase" from a 10% interest rate, then we know that the interest rate of 10% has increased by 0.10% (the absolute change) to a 10.1% rate.