An affix is morpheme that attaches itself to a root word to form a new word. For example, the adjective clear can be turned into an adverb by adding the affix -ly: clearly.
There are two broad categories off affixes: grammatical affixes and derivational affixes
Grammatical affixes form new words, where as grammatical affixes
IF #s THEN
IF s# THEN
”If the word begins with s, add se-.
Else if it ends with s, add -e.
In all other cases add s-.