Unfortunately, now you have to unlearn it! In my haste I often rely on the spell checker to alert me to my mistakes. Unfortunately spell checkers can only identify words that they do not find in their dictionaries, they cannot tell that you have correctly spelled one word when you intended to use a different word. Decadent is spelled in English as you say it should be, decedent is also a valid English word however:

de·ce·dent

[dih-seed-nt]
–noun Law .
a deceased person.

Origin:
1590–1600; < L dēcēdent- (s. of dēcēdēns ) departing, withdrawing, prp. of dēcēdere. See decease, -ent


My bad, sorry.



Ken