Six pairs of terms this site's own tools get confused for most often, disambiguated in plain language, each linking to whichever calculator actually matches what you mean.
A percentage point is a plain subtraction between two figures that are already percentages, a rate moving from 8% to 6% is a 2 percentage point drop. A percent (or percentage) is a proportional change measured against a starting value, that same move from 8% to 6% is a 25% decrease, because 2 divided by 8 is 0.25.
A discount is typically a temporary promotional price cut, a sale, a coupon, a limited-time offer. A markdown is a permanent reduction in a retail listing price, usually for clearance or discontinued stock, with no expectation the price goes back up.
Depreciation is a scheduled, rate-based projection of an asset's value over time, calculated forward from a known starting value and years, the method accountants and asset planners use. Value loss is a one-time calculation between two already-known values (what something cost, what it's worth now), with no schedule or projection involved.
These use the identical formula. Relative change is the term used in measurement and scientific contexts, comparing an observed reading to a reference or theoretical value. Percentage change is the same calculation applied to everyday business and personal comparisons, a starting value and an ending value.
Percentage difference compares two values with no defined before-and-after, dividing by their average, swap the two values and the answer doesn't change. Percentage decrease is directional: it has a defined original and new value, divides by the original, and swapping the two values changes both the sign and the meaning of the result.
percentage difference calculator · percentage decrease calculator
A simple growth rate compares only the start and end values, ignoring how many periods passed between them. CAGR (compound annual growth rate) spreads that same total growth evenly across however many years or periods it took, answering "what steady annual rate would produce this same result." CAGR is always lower than the simple total growth rate whenever more than one period is involved.
Every term on this page either is a variant of percentage decrease, is regularly confused with it, or is the direct opposite of it. Untangling which one actually applies to your numbers is usually the fastest way to land on the right calculator on the first try, rather than computing a plausible-looking answer with the wrong formula.