While writing about a factory that produces pipes, I needed to refer to how the metal was melted and put into molds/moulds. Which one is it, and is there a correct spelling or are both acceptable?


"mold" is the US spelling, "mould" is the British English spelling. No other difference.

Same applies for other meanings of mould/mold, i.e the fungus that grows on rotting substances, for example.

  • 3
    We revolted because the Redcoats stole our 'u's. – Oldcat May 21 '14 at 23:26

I'm from upstate New York and was schooled that 'mold' is the stuff that causes spoilage. 'Mould' is to form or shape. Moulding is the process of forming something or the formed piece itself, as in architectural moulding. A few years ago, our area finally got a Lowes store. I actually laughed out loud when I saw they had a sign claiming they had a 'molding' department! Yikes! Also a bit perplexed by all of the Spanish signage, especially since even our highway signs are written in English and French as we're only a few yards from Quebec.


Mould is to mold as colour is to color.


The Online Etymology Dictionary has "mould: see mold(2)", where 2 is the sense for fungus, however, mould is the accepted spelling in British English for all senses. Likewise mold in American English.

The three senses have interesting derivations, and I was not aware of the third one before now: http://www.etymonline.com/index.php?term=mold

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    John Brown's body lies a-mold'ring in the grave. – GEdgar Aug 12 '11 at 21:51
  • @GEdgar ah! John Brown's body lies a-crumbling in the grave. I previously thought "a-mold'ring" meant there was fungus growing on it. – John Ferguson Aug 17 '11 at 15:10
  • Sense 3 is presumably the one used in leaf mould which is more common than *mould*(3) on its own. It's also called "leaf mulch" even though it can be used as potting compost as well as mulch, presumably to avoid the connotations of *mould*(2). Apparently leaf mould is actually made by fungi (unlike normal compost which is mainly bacteria), giving a nice is coincidental link between 2 of the meanings – Chris H Nov 28 '13 at 14:49

Personally I have always used, perhaps was taught, that mold is the organic nasty stuff that makes you throw out food or apply bleach to kill it in the shower. (1) Moulding is what trims the walls of your house or is (2) a process using a 'mould' to form Jello, plastic, bricks or anything into a permanent or semi-permanent shape. Moulding can also be used to describe the act of creating character. Much like gild vs guild, I imagine; which someday may be used interchangeably also, since guild is rarely used anymore. Conversely the English 'smoulder' and American 'smolder' are like 'colour' and 'color', just an easy way to identify the educational system of the writer.

Being an 'old' English Major I dislike the modern impreciseness of the language that (especially American) English has acquired over the years, in particular the acceptance of i.e. 'forwards' instead of 'forward' or 'afterwards' instead of 'afterward'. Either are deemed acceptable in modern usage but I find the usage of the plural 's' on either word superfluous.


There seems some need to distinguish a fungus from a thing you pour jello into. I like "mold" for the former and "mould" for the latter and some use the words that way. Dictionaries just codify what's being done. So, why not choose the usage that makes sense and know the dictionary will eventually catch up?

James (Jim) Minard PhD

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