I am confused when the spellings "tion", "sion", and "cion" are used in words that contain the "shun" sound.

Are there any rules to help me understand when to use the correct spelling in a word?

  • 8
    There are some governing rules (heavily tempered by random accidents of history) but for your (practical) purposes, the solution is to simply look up each word, in a dictionary, as needed, until exposure, experience, and practice have permitted you to commit the spellings of the words to memory. That's how native speakers do it (or, in the case of certain native speakers, never do..). In other words: don't try to predict the right answer: English orthography is notoriously unpredictable. Just look up the right answer, in an authoritative reference.
    – Dan Bron
    May 2, 2015 at 18:51
  • I don't understand this answer, if it's prounounced as in addition it's tion and if explosion it's sion, what is the sound you are hearing that differentiates these two? Because in trying to teach my daughter to differentiate I can't clearly signify to her a sound difference, if we could clearly hear the sound difference it would be simple wouldn't it?
    – user201378
    Oct 17, 2016 at 11:38
  • 1
    @Sulamaye In addition the sound is unvoiced but in confusion it is now voiced.
    – tchrist
    Feb 25, 2017 at 6:37

1 Answer 1


Here are the main guidelines to choose the right suffix among -sion, -tion, and -cion. The first two are the more common while -cion is actually quite rare. (Lexico powered by Oxford)

Words ending in -sion

If the ending is pronounced as in confusion, then it should be spelled -sion. Here are some examples: collision; division; revision; persuasion; explosion; decision;seclusion.

When the ending comes after an -l, it's always spelled -sion: compulsion; revulsion; expulsion; emulsion; propulsion.

When the ending follows an -n or -r, it's often spelled -sion, especially if the word is related to one that ends in -d or -se. For example: immersion (from immerse); comprehension (from comprehend). Here are some more examples: aversion; conversion; apprehension; diversion; extension; version.

Nouns based on words that end in -ss or -mit always end in -sion: permission comes from permit and discussion comes from discuss Here are some more examples: commission; expression; aggression; admission; succession; impression; emission.

Words ending in -tion

If the ending is pronounced as in station, then it's spelled -tion. For example: addition; duration; nation; solution; ambition; edition; caution; position.

If the noun is related to a word ending in -ate, then the ending will be -ation, e.g. donation (from donate) or vacation (from vacate). Here are some more examples: accommodation; location; creation; rotation; education; mediation.

If the ending comes after any consonant apart from -l, -n, or -r, then the ending is spelled -tion: action; connection; reception; affection; interruption; description; collection; infection; deception.

After -n and -r, the ending can be -tion or -sion. It's more likely to be -tion if the word's related to another one that ends in -t or -tain, e.g. assertion (from assert) or retention (from retain). Here are some more examples: exertion; distortion; abstention; invention.

Words ending in -cion

There are just two common nouns that end in -cion: suspicion and coercion.

  • 1
    very helpful. I learned them just by experience, but your rules seem usable even by spelling bee contestants. Now if only there were a simple rule, or set of rules, for -ence/-ent vs. -ance/-ant! May 3, 2015 at 8:46
  • 2
    Of course suspicion comes from suspect and coercion from coerce so it's pretty obvious where the c comes from.
    – BoldBen
    Oct 17, 2016 at 14:23
  • Although you have inspect/inspection, so suspect/suspicion can't be used as a guide.
    – Stuart F
    Oct 27, 2020 at 11:43
  • @BrianHitchcock Now if only there were a simple rule, or set of rules, “There are no rules in English, only guidance. Some guidance looks like a rule; it probably isn't."
    – Greybeard
    Oct 27, 2020 at 20:44

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