Q
Abbreviation with 3 meanings
| Stands for | Rational numbers |
|---|---|
| Meanings | 3 |
| Categories | Units & Measurements |
| Also written | q |
Q has three meanings. The most common are Rational numbers (math) and Quecto- (10^-30) (metric and SI unit); it can also stand for Quetta- (10^30).
Meanings of Q at a glance
| # | Q stands for | Context |
|---|---|---|
| 1 | Rational numbers | Units & Measurements › Math |
| 2 | Quecto- (10^-30) | Units & Measurements › Metric and SI Unit |
| 3 | Quetta- (10^30) | Units & Measurements › Metric and SI Unit |
1. Rational numbers
Units & Measurements · Math Abbreviations
Written ℚ in blackboard bold, this is the set of all fractions p/q of integers with q not zero. The letter comes from quotient, a choice credited to Giuseppe Peano in 1895.
Example: The square root of 2 is not in Q, a fact known since ancient Greece.
Q is countable even though it is dense on the number line, with a rational between any two reals. The proof that the square root of 2 is irrational is traditionally attributed to the Pythagoreans. In field theory, Q is the smallest field of characteristic zero.
2. Quecto- (10^-30) (q)
Units & Measurements · Metric and SI Unit Abbreviations
The smallest SI prefix, 10^-30, adopted in 2022. Its standard illustration is the electron, whose mass is about 911 quectograms.
Example: Textbooks now quote the electron mass as about 911 qg when showcasing the new prefixes.
The name loosely recalls Latin decem, ten, since 10^-30 is 1000^-10. With quecto- and quetta-, the SI prefixes span 60 orders of magnitude. Lowercase q should not be confused with capital Q (quetta-) or with the quintal (q), a 100 kg agricultural unit still used in parts of Europe and India.
3. Quetta- (10^30)
Units & Measurements · Metric and SI Unit Abbreviations
The largest SI prefix, 10^30, added in 2022. Jupiter's mass is about 1.9 quettagrams, and the prefix gives a name to the quettabyte, 10^30 bytes.
Example: Jupiter's mass, about 1.9 Qg, makes it by far the heaviest planet in the solar system.
Proposed by metrologist Richard Brown of the UK's National Physical Laboratory and approved in November 2022, the name loosely recalls Latin decem, ten (1000^10). With quetta- and quecto-, SI prefixes now span 60 orders of magnitude. Capital Q is the prefix; lowercase q is its tiny counterpart, quecto-.
Related abbreviations
More math abbreviations
- pct – Percent
- PDE – Partial differential equation
- PEMDAS – Parentheses, Exponents, Multiplication/Division, Addition/Subtraction
- Pf – Proof
- QED – Quod erat demonstrandum (which was to be demonstrated)
- R – Real numbers
- Re – Real part
- resp. – Respectively
See all 91 math abbreviations →