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One (1) Unit Definition
One, also called unit, and unity is a number, and a numerical digit used to represent that number in numerals. It represents a single entity, the unit of counting or measurement. For example, a line segment of unit length is a line segment of length 1. One is the smallest positive integer. It is also sometimes considered the first of the infinite sequence of natural numbers, followed by 2, although by other definitions 1 is the second natural number, following 0.
Overview
The fundamental mathematical property of 1 is to be a multiplicative identity, meaning that any number multiplied by 1 returns that number. Most if not all properties of 1 can be deduced from this. In advanced mathematics, a multiplicative identity is often denoted 1, even if it is not a number. 1 is by convention not considered a prime number. Although universal today, this was a matter of some controversy until the mid-20th century.
SI Prefixes
Here is a table of the SI prefixes and some of their properties:
Name & Symbol |
Base 10 |
Decimal |
English Word |
Adoption |
|
Short Scale |
Long Scale |
||||
| Quetta (Q) | 1030 |
1,000,000,000,000,000,000,000,000,000,000 |
Nonillion |
Quintillion |
2022 |
| Ronna (R) | 1027 |
1,000,000,000,000,000,000,000,000,000 |
Octillion |
2022 |
|
| Yotta (Y) | 1024 |
1,000,000,000,000,000,000,000,000 |
Septillion |
Quadrillion |
1991 |
| Zetta (Z) | 1021 |
1,000,000,000,000,000,000,000 |
Sextillion |
Trilliard |
1991 |
| Exa (E) | 1018 |
1,000,000,000,000,000,000 |
Quintillion |
Trillion |
1975 |
| Peta (P) | 1015 |
1,000,000,000,000,000 |
Quadrillion |
Billiard |
1975 |
| Tera (T) | 1012 |
1,000,000,000,000 |
Trillion |
Billion |
1960 |
| Giga (G) | 109 |
1,000,000,000 |
Billion |
Milliard |
1960 |
| Mega (M) | 106 |
1,000,000 |
Million |
1873 |
|
| Kilo (k) | 103 |
1,000 |
Thousand |
1795 |
|
| Hecto (h) | 102 |
100 |
Hundred |
1795 |
|
| Deca (da) | 101 |
10 |
Ten |
1795 |
|
| One (1) | 100 |
1 |
One |
- |
|
| Deci (d) | 10-1 |
0.1 |
Tenth |
1795 |
|
| Centi (c) | 10-2 |
0.01 |
Hundredth |
1795 |
|
| Milli (m) | 10-3 |
0.001 |
Thousandth |
1795 |
|
| Micro (µ) | 10-6 |
0.000001 |
Millionth |
1873 |
|
| Nano (n) | 10-9 |
0.000000001 |
Billionth |
Milliardth |
1960 |
| Pico (p) | 10-12 |
0.000000000001 |
Trillionth |
Billionth |
1960 |
| Femto (f) | 10-15 |
0.000000000000001 |
Quadrillionth |
Billiardth |
1964 |
| Atto (a) | 10-18 |
0.000000000000000001 |
Quintillionth |
Trillionth |
1964 |
| Zepto (z) | 10-21 |
0.000000000000000000001 |
Sextillionth |
Trilliardth |
1991 |
| Yocto (y) | 10-24 |
0.000000000000000000000001 |
Septillionth |
Quadrillionth |
1991 |
| Ronto (r) | 10-27 |
0.000000000000000000000000001 |
Octillionth |
2022 |
|
| Quecto (q) | 10-30 |
0.000000000000000000000000000001 |
Nonillionth |
Quintillionth |
2022 |
Other Prefix Unit Definitions
- Atto (a)
- Centi (c)
- Deca (da)
- Deci (d)
- Deka (da)
- Exa (E)
- Exbi (Ei)
- Femto (f)
- Gibi (Gi)
- Giga (G)
- Hecto (h)
- Kibi (Ki)
- Kilo (k)
- Mebi (Mi)
- Mega (M)
- Micro (µ)
- Milli (m)
- Nano (n)
- One (1)
- Pebi (Pi)
- Peta (P)
- Pico (p)
- Qubi (Qi)
- Quecto (q)
- Quetta (Q)
- Robi (Ri)
- Ronna (R)
- Ronto (r)
- Tebi (Ti)
- Tera (T)
- Yobi (Yi)
- Yocto (y)
- Yotta (Y)
- Zebi (Zi)
- Zepto (z)
- Zetta (Z)
Convert to Another Prefix Unit
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Sources
“1.” Wikipedia, Wikimedia Foundation, 8 Apr. 2020, en.wikipedia.org/wiki/1.