Is there a difference in meaning between somnoler and sommeiller and when should I use one and when other?


You can get a lot of descriptions from the Trésor de la langue française informatisé. Somnoler and sommeiller can be used as synonyms in some contexts, especially talking about inanimate beings (a town). There are however a few subtle differences. Substantives sommeil and somnolence indeed have different meanings.

I will restrict to human beings, and try to highlight when the meanings differ.

Old meanings for sommeiller include sleep, and death. It now denotes a shallow sleep, possibly short, either close to awakening or falling asleep. Or an inactive, passive state.

Somnoler, to what I understand and use, is closer to half-sleep, meaning partly awake, partly sleepy. You may use somnoler when you are doing something, and gently falling asleep (chosen examples for TLF: "être temporairement inutilisé", "s'engourdir", "s'endormir en faisant quelque chose".).

For instance, I would say:

  • le conducteur somnolait au volant (en roulant),


  • le conducteur sommeillait au volant de sa voiture (à l'arrêt).

One talks about "somnolence au volant". While not a proof, the expression "sommeille au volant" seems much less frequent with a common search engine than "somnole au volant".

To make it short, sommeiller often denotes a steady state, somewhere between the state of sleep and wake. While somnoler is more evolutive (slowly oscillating between wake and sleep), or denotes a temporary state or situation. Sommeiller can be short or shallow, but somnoler is more intermittent.

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  • As said in gustav's answer, I would not use "sommeiller" this way... I would only use "somnoler" to mean "a steady state, somehow halfway between sleep and wake"... By the way, your links are broken... – Random Aug 24 '16 at 7:18
  • @Random I have added an example, and subtle differences. Could you tall me more about "I would not use "sommeiller" this way"? – Laurent Duval Aug 24 '16 at 7:55
  • the only 2 ways I would use "sommeiller" are in "réveille le lion qui sommeille en toi", and "j'ai sommeil"... I would never use "sommeiller" in a direct form (as in your 2nd example "le conducteur sommeillait au volant de sa voiture (à l'arrêt)."), it sounds very strange to me... – Random Aug 24 '16 at 8:52
  • From Le petit Robert: "Dans le break, en revenant, tous les hommes, hormis Jean, sommeillaient" (Maupassant). I agree this may sound a bit old-fashioned. The example for somnoler is "Des vertus somnolent, faute de pouvoir se manifester" (Daudet), where the meaning is about the same as sommeiller. – Laurent Duval Aug 24 '16 at 9:01

In France, no one use "sommeiller", you have to use "somnoler" when you are about to sleep.

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  • Welcome to FrenchLanguage. Thanks for taking the time to answer, but I think that "Sommeiller" take two "m" and is actually used more often than "somnoler" by french speaker. – Jylo Aug 23 '16 at 20:06
  • Ok, I asked an older french friend who said to me that "Sommeiller" does exist but it's not really use. "Sommeiller" means you are sleeping, or trying to, it's a bit fancy. PS: I'm french from Paris and I never heard about "Sommeiller" before. ,, – gustav.b Aug 23 '16 at 21:23
  • @Pierre.Sassoulas In France, I would never use "sommeiller" with this meaning. The only way I would use it is as in "réveille le lion qui sommeille en toi", which is very different... – Random Aug 24 '16 at 7:16
  • Ok, no problem for expressions – gustav.b Aug 24 '16 at 12:27

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