Editing Module:Convert/documentation/conversion data/introduction (section)

== Notes on units ==
=== Energy and torque ===
By convention, units written as force-distance (such as lbft or kgf.m) are torque, and those written as distance-force (such as ftlbf) are energy. See [[WP:MOSNUM#Unit names]] and the [[WT:Manual of Style/Dates and numbers/Archive 135#Foot-pounds and pound-feet|discussion]], and see [[Pound-foot (torque)]] and [[Foot-pound (energy)]].

However, some topics use traditional units that conflict with the above convention. To handle these, [[Module:Convert/makeunits]] includes a <code>specials</code> table that adds an "alttype" (alternate type) field to certain whitelisted units. The alttype field allows conversion between units of different type, provided each unit is whitelisted to allow the conversion.

As at December 2013, the following energy units have alttype = "torque" (the first line consists of different units, while the second line consists of aliases for units in the first line):
*ftlb, ftlb-f, ftlbf, inlb, inlb-f, inlbf, inoz-f, inozf
*ft.lbf, ft·lb-f, ft·lbf, in.lb-f, in.lbf, in.oz-f, in.ozf, in·lb-f, in·lbf, in·oz-f, in·ozf

The following torque units have alttype = "energy":
*Nm
*N.m, N·m

For example, the following conversion works despite the fact that Nm is torque and ftlbf is energy:
*<code><nowiki>{{convert|1|Nm|ftlbf}}</nowiki></code> → {{convert|1|Nm|ftlbf}}