Liza,
I didn't think there was such a word, until I did a search and found this:
By derivation, all words form 2 structural classes:
1. simplexes (non-derived)
2. complexes (derivatives) which in their turn may be divided into:
· sufficial
· prefixal
· conversions
· compounds
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Apparently, in the field of lexicology, the branch of linguistics concerned with the meaning and use of words, "sufficial" is an alternative spelling for "suffixal".
suffixal (sufficial) adj. - occuring at the end of a word
Of course, it is also possible that "sufficial" is just a misspelling.