I'm doing some verb to derived word conversions and I'm struggling with keeping the T or converting it to a C in some verbs ended with T:

Exhibit -> Exhibition

Perfect -> Perfection

Benefit -> Beneficial

I have done a bit of research on beneficial and that's what I've found, no common patterns at all.

Is there any rule to make this conversion?


2 Answers 2



I found a site that offers a rule of thumb for spelling words ending in -tial/-cial which doesn't even require you to know the spelling of the related verb. It is

Use -cial after a vowel, like after the vowel ‘o’ in social, ‘e’ in special, ‘i’ in beneficial

Use -tial after a consonant, especially, after ‘n’ in substantial, essential, ‘r’ in partial


Memorise/memorize these seven exceptions: financial, commercial, provincial, initial, spatial, palatial, controversial

(from www.howtospell.co.uk, by Joanne Rudling)

This list of exceptions is probably sufficient for common words. You should know that it is not comprehensive; it excludes for example adventitial, solstitial, preputial; internuncial, uncial; and probably also some other rare words. Despite the presence of these exceptions, this does seem to be a real trend, based on a comparison of words that end in -tial and words that end in -cial (Morewords.com).


There are only two common words in English that end in -cion: suspicion (related to the verb suspect) and coercion (related to the verb coerce). There are many words spelled with -tion, which can come after vowel letters (as in creation) or consonant letters (as in perception).

You might also be interested in the answer to this question about when to use the spellings -sion, -⁠tion and -cion.

  • Seems so interesting , I'll take a look at it, thanks!
    – Aritz
    Commented Feb 28, 2016 at 18:08

The first poster was right (but not helpful) when he said this is an 'irregular' formation. So I don't have a rule to give you, but at least there is an explanation for the irregularity; some forms of the words benefit have always had a 'c' in them.


So this isn't a weird case of adding a 't', it's a case of benefice losing its 'c' over time.


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