Editing Parts-per notation (section)

==Parts-per expressions==<!-- This specific section is linked from [[Uranium]] and other articles; please do not rename this section. In the following equivalencies, it is assumed that one xxxx of water has a volume of 0.05 ml (20 xxxx per milliliter).-->
{| class="wikitable" style="font-size:85%;line-height:0.9;text-align:center;margin-left:1ex;float:right;"
!style="padding:0 1px;"|1 of →<br />= ⭨<br />of ↓ &nbsp;
!per<br />cent<br />(%)
!per<br />mille<br />(‰)
!per<br />10,000<br />(‱)
!per<br />100,000<br />(pcm)
!per<br />million<br />(ppm)
!per<br />billion<br />(ppb)
|-
!%
|1||0.1||0.01||0.001||0.0001||{{10^|-7}}
|-
!‰
|10||1||0.1||0.01||0.001||{{10^|-6}}
|-
!‱
|100||10||1||0.1||0.01||{{10^|-5}}
|-
!pcm
|1,000||100||10||1||0.1||0.0001
|-
!ppm
|10,000||1,000||100||10||1||0.001
|-
!ppb
|{{10^|7}}||{{10^|6}}||{{10^|5}}||10,000||1,000||1
|}
{{visualisation_parts_per.svg}}
*''One part per [[100|hundred]]'' is generally represented by the [[percent sign]] (%) and denotes [[percentage|one part per 100 ({{10^|2}}) parts]], and a value of {{10^|-2}}. This is equivalent to about fourteen minutes out of one day.
{{anchor|Thousand}}
*''One part per [[1000 (number)|thousand]]'' should generally be spelled out in full and '''not''' as "ppt" (which is usually understood to represent "parts per [[trillion (short scale)|trillion]]"). It may also be denoted by the [[per mille|permille]] sign (‰). Note however, that specific disciplines such as oceanography, as well as educational exercises, do use the "ppt" abbreviation. "One part per thousand" denotes one part per 1,000 ({{10^|3}}) parts, and a value of {{10^|-3}}. This is equivalent to about ninety seconds out of one day.
*''One part per [[ten thousand]]'' is denoted by the [[permyriad]] sign (‱). Although rarely used in science (ppm is typically used instead), one permyriad has an unambiguous value of one part per 10,000 ({{10^|4}}) parts, and a value of {{10^|-4}}. This is equivalent to about nine seconds out of one day. <br/>In contrast, in [[finance]], the [[basis point]] is typically used to denote changes in or differences between percentage interest rates (although it can also be used in other cases where it is desirable to express quantities in hundredths of a percent). For instance, a change in an interest rate from 5.15% per annum to 5.35% per annum could be denoted as a change of 20 basis points (per annum).<!--NOTE TO EDITORS:

Unlike the % symbol, which constitutes a formatting exception to the rule of the SI, a space goes between the value and both the permille and permyriad symbols (‰ and {{unicode|‱}}). Besides adhering to the rule of the SI, this is also good technical writing practice as it helps to distinguish these two less-common symbols from the percent symbol.

--> As with interest rates, the words "per annum" (or "per year") are often omitted. In that case, the basis point is a quantity with a dimension of (time<sup>−1</sup>).<ref>{{Cite web|url=https://corporatefinanceinstitute.com/resources/fixed-income/basis-points-bps-definition/|title=Basis Points (BPS)|website=Corporate Finance Institute}}</ref>
* ''One part per [[100,000|hundred thousand]]'', ''[[per cent mille]]'' ('''pcm''') or ''milli-percent'' denotes one part per 100,000 ({{10^|5}}) parts, and a value of {{10^|-5}}. It is commonly used in [[epidemiology]] for mortality, crime and disease prevalence rates, and nuclear reactor engineering as a unit of reactivity. In [[time measurement]] it is equivalent to about 5 minutes out of a year; in [[distance measurement]], it is equivalent to 1&nbsp;cm of error per km of distance traversed.
{{anchor|ppm}}
* ''One part per [[1,000,000|million]]'' ('''ppm''') denotes one part per 1,000,000 ({{10^|6}}) parts, and a value of {{10^|-6}}. It is equivalent to about 32 seconds out of a year or 1&nbsp;mm of error per km of distance traversed. In [[mining]], it is also equivalent to one [[gram]] per [[metric ton]], expressed as g/t.
{{anchor|ppb}}
* ''One part per [[1,000,000,000|billion]]'' ('''ppb''') denotes one part per 1,000,000,000 ({{10^|9}}) parts, and a value of {{10^|-9}}. This is equivalent to about three seconds out of a [[century]].
{{anchor|ppt}}
* ''One part per [[Orders of magnitude (numbers)#1012|trillion]]'' ('''ppt''') denotes one part per 1,000,000,000,000 ({{10^|12}}) parts, and a value of {{10^|-12}}. This is equivalent to about thirty seconds out of every million years.
{{anchor|ppq}}
* ''One part per [[Orders of magnitude (numbers)#1015|quadrillion]]'' ('''ppq''') denotes one part per 1,000,000,000,000,000 ({{10^|15}}) parts, and a value of {{10^|-15}}. This is equivalent to about two and a half minutes out of the [[age of the Earth]] (4.5 billion years). Although relatively uncommon in analytical chemistry, measurements at the ppq level are sometimes performed.<ref>
Measurements of [[Polychlorinated dibenzodioxins|dioxin]] are routinely made at the ''sub''-ppq level. The [[United States Environmental Protection Agency|U.S. Environmental Protection Agency]] (EPA) currently sets a hard limit of 30&nbsp;ppq for dioxin in drinking water but once recommended a voluntary limit of 0.013&nbsp;ppq. Also, radioactive contaminants in drinking water, which are quantified by measuring their radiation, are often reported in terms of ppq; 0.013&nbsp;ppq is equivalent to the thickness of a sheet of paper versus a journey of {{val|146000}} trips around the world.<sub>&nbsp;</sub></ref> <!-- EDITORS NOTE REGARDING {{val|146000}} TRIPS AROUND THE WORLD:

The analogy of paper thickness vs. 146k trips around the world may be so wildly counterintuitive that the statement might seemingly be in error, but please do not change the statement without first understanding the below math (shown here with excess precision):

Paper thickness = 0.0030 inch = 0.0000762 m (0.003 × 25.4 mm/inch ÷ 1,000 mm/m)
Earth's mean circumference = 40,041,470 m

In then follows that...
[[File:Image-Olympic Pool Munich 1972, color adj.jpg|thumb|One part per [[trillion (short scale)|trillion]] (1&nbsp;ppt) is a proportion equivalent to a drop of water diluted into 400 [[Olympic-size swimming pool]]s.]]

In [[science]] and [[engineering]], the '''parts-per notation''' is a set of pseudo-units to describe

146,386.7 trips × 40,041,470 m × 0.013E-15 = 0.0000762 m = 0.0030 inch = paper thickness
-->