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One states a subtraction; the other states a tolerance. The second contains the first, which is where the confusion starts.
− subtracts, or marks a negative value. ± means 'give or take' — a tolerance, a margin of error, or both roots of a quadratic. A measurement written 20 ± 2 spans 18 to 22; written 20 − 2 it is simply 18.
The plus–minus sign contains a minus stroke beneath a plus.
Drawn from the visual attributes recorded for each symbol. Only traits the two records disagree about are listed.
| Trait | Minus sign | Plus–minus sign |
|---|---|---|
| Built from | lines and dots | crosses, lines and dots |
| Symmetry | bilateral | vertical |
| Minus sign | Plus–minus sign | |
|---|---|---|
| What it states | Subtraction, or a negative quantity | A range either side of a value |
| Read aloud as | 'minus' | 'plus or minus' |
| Typical use | Arithmetic, temperatures below zero, negative balances | Measurement tolerance, margin of error, quadratic roots |
| Shape | A single horizontal stroke | A plus sign above a horizontal stroke |
| Unicode | U+2212 | U+00B1 |
| Relationship (from Symbolwise's records) | Commonly confused with Plus–minus sign — The plus–minus sign contains a minus stroke beneath a plus. | Commonly confused with Minus sign — Reciprocates the minus sign's warning: the plus–minus sign contains a minus stroke.; Composed of Minus sign — The lower stroke. |
Unicode Code Chart: Mathematical Operators (U+2200–U+22FF)
The Unicode Consortium · retrieved 2026-07-30
Authoritative for the character's code point, name and block only. Unicode assigns identity; it does not define what a symbol means in use.
Unicode Code Chart: Latin-1 Supplement (U+0080–U+00FF)
The Unicode Consortium · retrieved 2026-07-30
Authoritative for the character's code point, name and block only. Unicode assigns identity; it does not define what a symbol means in use.
Wikipedia · retrieved 2026-07-30
Tertiary reference. Used for widely-agreed identity and origin summary, not for contested detail or exact dates.
Wikipedia · retrieved 2026-07-30
Tertiary reference. Used for widely-agreed identity and origin summary, not for contested detail or exact dates.
Alpha is a Greek letter and stands for a quantity — an angle, a coefficient, a significance level. The proportionality sign is an operator and stands between two quantities to say they keep a constant ratio. The drawings differ in that the proportionality sign's right-hand stroke runs out in an open curve rather than closing into the letter's tail.
Look at the left-hand edge. A straight flat back is an AND gate: the output is true only when every input is. A curved concave back is an OR gate: true when any input is. Everything else about the shapes is similar, which is why the back edge is worth checking deliberately rather than at a glance.
Look at what follows. A prefix never stands alone — it is glued to a unit symbol, as in kW or kg. A constant stands by itself in an equation. Careful physical writing subscripts the constant as k_B for exactly this reason, and the kelvin's capital K is a third claimant to the same letter.
Length is the tell. A crescendo hairpin is drawn long, below a stave, and spans the passage it applies to — its extent *is* the instruction. A less-than sign is one character wide and sits between two values. If it stretches, it is music; if it fits between two numbers, it is mathematics.