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? Answer -tial/-cial 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 s o cial, ‘e’ in sp e cial, ‘i’ in benef i cial Use -tial after a consonant, especially, after ‘n’ in substa n tial, esse n tial, ‘r’ in pa r tial [...] 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...