I've come across two spellings for this word. Siphon and syphon are apparently both correct. English is not my first language and this word is not used often in practice, especially in written form. I am very curious about this. Is there any reason to prefer one over the other? And which spelling would be more common? Is it a regional thing (like maybe American like one and British the other) or something else. I wonder if this is a specific case of more common interchange between i and y in some words - which would be interesting.

Wikipedia suggests that siphon may be more common spelling.

  • A Google Ngram suggests that it's five times as popular overall (though this wasn't always the case). Mar 26, 2014 at 19:57
  • Oh cool, maybe syphon is the older version
    – Chemist
    Mar 26, 2014 at 20:09
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    Very good question! The spelling with a y is completely unetymological and doesn’t seem to occur anywhere but English—even Dutch (where long i gives ij, which is often confused with y in writing) has sifon with an i. It seems at some point in the history of the English language, someone just decided this word would look nicer with a y than with an i, and the spelling stuck. Mar 26, 2014 at 21:02
  • 1
    Somewhat similar question: Cipher vs. Cypher
    – herisson
    Oct 3, 2015 at 12:20
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    The "ph" makes it look Greek in origin, and the "y" seems to go well with that look. E.g. "polyphony", "symphony". "Python" also comes to mind... Oct 9, 2015 at 6:59

3 Answers 3


Both are in the "Oxford Advanced Learners Dictionary" so I don't think there's any strong reason to prefer one over the other.

As a native speaker of English I would say 'siphon' is the more commonly used spelling (for example see this Guardian article: http://www.theguardian.com/science/blog/2010/may/10/dictionary-definition-siphon-wrong).

I personally find 'syphon' much more aesthetically pleasing though.


Siphon is the common and preferred form

My very big dictionary (The American Heritage Dictionary of the English Language, 4th edition) contains no distinct entry for syphon. The entry for siphon reads as follows:

si-phon also sy-phon n. 1. A pipe or tube fashioned or deployed in an inverted U shape and filled until atmospheric pressure is sufficent to force a liquid from a reservoir in one end of the tube over a barrier higher than the reservoir and out the other end. 2. Zoology A tubular organ, especially of aquatic invertebrates such as squids or clams, by which water is taken in or expelled. v. -phoned, -phon-ing, -phons -tr. To draw off or convey through as if through a siphon. -intr. To pass through a siphon. adj. -si'phon-al, si-phon'ic [Middle English, from Latin sipho, sipohon-, from Greek siphon.]

All of these variants use the siphon form where applicable, and while my keyboard doesn't translate the Latin and Greek characters properly, the way they are displayed in my book is visually similar to the letter I. The alternate spelling is listed as an alternate and then no further attention is paid to it. Study of additional dictionaries might be necessary to determine if this is standard or stylistic, but from the commentary I think we can safely determine that siphon is standard and syphon is an anomaly that no longer sees common use.

Of course, anomalous spelling can serve a stylistic or atmospheric function when used appropriately. I would recommend using siphon primarily and only using syphon when it serves a specific purpose.


In my humble opinion syphon is the English spelling and siphon the american so it would depend on your audience. Obviously all English speaking computers are american so they will always prefer the i version.

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    There may be regional preferences for one form or another, but I don't see how that would be a matter of opinion. It would be a fact; or if it's not true, a misimpression. Do you have evidence showing that "syphon" is considered a British/English spelling, and "siphon" an American spelling? By the way, it's not true that all spell-checkers use American spelling. It can be a bit tricky to set it up, but Microsoft Word does have a U.K. English option.
    – herisson
    Oct 26, 2016 at 17:34
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    As far as I can tell, "syphon" is more common in the UK than it is in the US, but in both regions, "siphon" is more common than "syphon." This is what the Google ngram viewer shows: books.google.com/ngrams/…
    – herisson
    Oct 26, 2016 at 17:46
  • If this is true, it's right to say that the spelling "syphon" is associated with the UK to some degree, but it doesn't seem to be right to say that it is "the" English spelling: "siphon" is also an English spelling.
    – herisson
    Oct 26, 2016 at 17:47

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