Consider the following words as examples:

1) Version
2) Progression
3) Differentiation
4) Fission
5) Fusion
6) Insurance
7) Sure

I pronounce all these words with a 'sh' sound even though it is not explicit in written. I have heard people using some of these words with a 's' sound, especially #6. Both myself and the folks I have heard talking are non-native English speakers.

Are there any defined rules that tell when 's' or 'sh' sounds should be used?

  • 3
    "Version" and "fusion" are actually usually pronounced with a third sound, often represented in dictionaries by "zh," that is to the "z" sound what "sh" is to "s."
    – herisson
    Sep 1, 2015 at 12:43
  • 2
    In the dialect of English local to Hawaii, "s" is shifted to "sh" before "r", for instance in the word "street".
    – Greg Lee
    Sep 1, 2015 at 13:49
  • Your best tool is a pronunciation dictionary. If not, I'd listen to the online pronunciation that the online dictionaries offer. As already pointed out here, 'version' and 'fusion' are pronounced like 'division'. In such words ending in "-sion", the pronunciation is 'zhun', and not 'shun'. All other examples on your list have the sound of "sh".
    – Sankarane
    Sep 1, 2015 at 22:35
  • The people you've heard using S are just doing their own thing -- don't use them as a model for good pronunciation. All these words will have SH or ZH (depending on whether it is voiced or unvoiced). Sep 2, 2015 at 21:12

1 Answer 1


This comes with the usual warning about rules for English:

Rule .1. -ive makes s sound S. But -ion creates ZH unless after ss then SH.

massive s, (im-)passive s but (com-)passion sh, invasive s, but invasion zh,

adhesive s, but adhesion zh,

divisive s, but division zh, derisive s, but derision zh

(per-)missive s, dismissive s, derisive s, indecisive s & s, mission sh, indecision zh, derision zh,

explosive s, explosion zh, erosion zh

extrusion zh,

effusive s elusive s fusion zh, effusion zh, illusion zh, allusion zh

Rule .2. -tion makes SHn and the preceding vowel is (often) made long.

(indication sh)(station sh) (relation sh) (depletion sh) (contrition sh short -i-) (emotion sh)(motion sh) (devotion sh) (contribution sh),
But sometimes "s" (initiation, s?sh)

Rule .3. Visual is unusual.

  • 1
    How is "visual" unusual? (There's also "casual" that follows this pattern, and on the voiceless side, "consensual.")
    – herisson
    Sep 1, 2015 at 20:06
  • @sumelic , It was intended as a mnemonic linking zh to -al suffix, and there was going to be a play on casual zh and (causal z, mesal and occlusal;) with dorsal demonstrating the reversal of the rule. Currently waiting on the Muse,
    – Hugh
    Sep 1, 2015 at 20:33

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