Why is the letter l double in the inflections of the verb surveil?

It's not in those of (as)sail or veil, and AmE has canceled but mostly cancellation. It's a counterintuitive spelling similar to those of control.

No wonder some people write it as surveille

Per Decapitated Soul's answer to When is "L" doubled?:

The -l- after a digraph or a diphthong does not usually get doubled.


  • Prevail -> prevailed not prevailled.
  • Detail -> detailed not detailled.
  • Mail -> mailed not mailled.

Why is surveilled, surveilling an exception?

  • @DecapitatedSoul what do you call syllable exactly? what about sailed, assailed and veiled ?
    – GJC
    Oct 9, 2021 at 9:35
  • 1
    @herisson I am confused. Why is it still a duplicate even after your editing?
    – GJC
    Oct 9, 2021 at 11:31
  • In any event, it makes no difference to English, since (a) the /l/ isn't doubled, (b) the rule confuses digraphs and diphthongs, (c) there is no definitive rule. All spelling is just printers' conventions, which change with printing technology and don't change with the language. Oct 9, 2021 at 16:42
  • @herisson: You're right. I didn't realise there was a digraph there... I'll delete my comment. Oct 10, 2021 at 19:22

1 Answer 1


I'd guess it's because it is a back formation from surveillance, which is spelled with two Ls. As you noted, some people use the spelling surveille.

The noun surveillance remains much more common than any form of the verb:

enter image description here

(Google Ngram Viewer)

  • 1
    +1 surveillance is from French. Some few Amerians even pronounce it like "survey-ance".
    – GEdgar
    Oct 9, 2021 at 11:54

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