Words ending is -cial and -tial have exactly the same pronunciation ( /ʃəl̩/ shuhl ).
So how do you remember the spelling?
ANSWER
1. Use -cial when it comes after a vowel (a,e,i,o,u)
2. Use -tial when it comes after a consonant (n)
Amazing!
Is there a similar rule for ‘-tion’, ‘-sion’ and ‘-cian’? (shun /ʃən/ )
I will do some research and get back to you.