# Talk:Physical quantity

Active discussions
WikiProject Physics (Rated C-class, Top-importance)

## External link to Complex Unit Converter

A useful converter between SI and other units is available at http://AnalysisChamp.com/EEx/ExpEvalCV.asp. This converter is capable of performing complex conversions between any and all proper unit expressions and should be included as an external link to this article. MikeVanVoorhis (talk) 22:27, 5 June 2009 (UTC)

## CORRECTION needed

first word, second line:

"Formally....." is an ambiguous word, because following definition is NOT formal but informal

somebody probably meant " current, official, mainstream, aknowledged... definition " ?93.43.232.68 (talk) 07:10, 6 September 2011 (UTC)

## Generic term for, um, "unitend"?

I think I've discovered a hole in the English language. Let me draw a parallel to help explain it.

3 and 4 are numbers (positive integers if you want to be specific). But, when you see them in the form of a fraction — 3/4 — we have particular name for each of them IN THAT CONTEXT. 3 is the "numerator" and 4 is the "denominator".

Now consider a bunch of different measurements, such as:

• 2.54 centimetres

• 7 days

• 1.5 litres

• 12 ounces

• –40 degrees

The generic name for the words "centimetres", "days", "litres", "ounces", and "degrees" is "units". But what's the generic name for the numeric part of the measurement, the 2.54, 7, 1.5, 12, and –40? IOW, if any given measurement comprises an "X" and a unit of measure, what's the "X"?

Suggested answers when I inquired among my friends included "magnitude", "number", "numerical value", just plain "value", and "quantity", but each of those words is sufficiently generic that it can also be used in other contexts. What I was searching for (but which may not exist) is a word like "numerator", which of course is also a number, value, etc. but which is a specific KIND of number, value, etc. that only has meaning in the context of a fraction. I'm looking for the equivalent word that only has meaning in the context of a measurement.

For lack of a better term, I have used a placeholder term as the title of this section, drawing a parallel to "dividend" as "the number to be divided". Here the fake word "unitend" is taken to mean "the number to which the unit of measurement is to be applied". This is unsatisfactory for several reasons, not least of which is that my computer keeps trying to change it to "united". Does anyone have either (a) an official answer to this question or (b) a better suggestion?

Excuse me for my ignorance, but I'm new at this. I hope the requested 4 tildes go here: RichardSRussell (talk) 04:37, 1 December 2011 (UTC)

## Is "information" a physical quantity?

Is "information" a physical quantity? 125.253.44.20 (talk) 10:59, 28 May 2014 (UTC)

I believe not, at least formally. It would need some organization to define the quantity "ammount of information", like the International Committee for Weights and Measures defined "ammount of substance" (and made the mole its unit). Of course Wikipedia has no authority to do this.
I believe as of now the quantity "ammount of information" (measured in bits for example) is no diferent to the quantity "ammount of rocks" (measured in the hypothetical unit rck). 177.68.225.247 (talk) 21:55, 23 March 2017 (UTC)

Upon further research, it seems that the ISO/IEC 80000 does define some information-related quantities, including: storage capacity, storage size, information content, entropy. The referenced page also includes the statement
 Units that form part of the standard but not the SI include the units of information storage (bit and byte), units of entropy (shannon, natural unit of information and hartley), the erlang (a unit of traffic intensity) and units of level (neper and decibel).
Therefore I am inclined to say that information (as described in the Standard) is indeed a (physical) quantity, but it needs to be made clear what one means by "information".
I don't have sources but I also believe theses information-related quantities cited here are dimensionless.
--177.138.210.163 (talk) 04:20, 25 March 2017 (UTC)

If someone can confirm it, please add them. It would be a great adition to have information-related quantities among the current ones in the article.
177.138.210.163 (talk) 04:39, 25 March 2017 (UTC)

## Physical Quantity = Physical magnitude ??

First line says, A physical quantity (or "physical magnitude")....... As far as I know Physical quantity is a quantity which can have magnitude. But the line sort of confuses it. Even though it is only a pedantic query I think it is important to use correct words.

Contact '97 (talk) 11:42, 15 May 2016 (UTC)

Edited, replaced "number" with "magnitude" to the formula "Quantity is expressed by a Magnitude and a Unit" (where the unit can be of more than one kind, such as m/s). 2601:583:8205:9C20:111B:F58F:F00F:C787 (talk) —Preceding undated comment added 14:33, 3 August 2016 (UTC)

## Physical quantity vs. physical property

The article physical quantity essentially refers its definition to being a physical property, with the qualification of being quantified by measurement. This qualification, however, is already implied by physical property (...is any property that is measurable,...). Therefore, the articles appear to cover the same subject matter under different terms. Physical quantity, however, focusses mostly on units and measures, while physical property is more of a short philosophical discussion. Kbrose (talk) 11:51, 15 August 2017 (UTC)

The article uses a definition of physical quantity quoting the JCGM, which however is attributed there to the more generic definition for quantity, not just physical quantity. Kbrose (talk) 13:12, 15 August 2017 (UTC)

## POV tag

I tagged this article as POV mainly due to things like "...or operators like d in dx, are also recommended to be printed in roman type." Some people might recommend so, but others do not. –Deacon Vorbis (carbon • videos) 02:37, 9 March 2018 (UTC)

## Are plane angle and solid angle as base quantities

The "International System of Quantities base quantities" table here lists both plane angle (radian) and solid angle (steradian) as a base quantities. However the linked page (https://en.wikipedia.org/wiki/International_System_of_Quantities) lists these both as derived quantities. I am not sure which is correct, but this appears to be inconsistent. 24.117.28.229 (talk) 04:59, 19 December 2020 (UTC)