2. Definition
Suffix:
a group of letters that you add to the end of a word to make another word.
In the word 'slowly', '-ly' is a suffix.
/ˈsʌfɪks/
3. Noun suffixes
-er added to a verb is used for the person who does an activity: writer, worker, singer,... (sometimes -or, as in actor, sailor, supervisor,...)
-er/-or are also used for things which do a particular job: tin-opener, projector, ...
-er and -ee can contrast with each other, meaning "person who does something" (-er) and "person who receives or experiences the action" (-ee): employer/employee, ...
-(t)ion is used to make nouns from verbs: communication, pollution, admission, ...
4. Noun suffixes
-ist is also used for people who play musical instruments: pianist, violinist
-al is added to some verbs to make nouns: arrival, refusal,
-ness is used to make abstract nouns from adjectives: happiness, goodness, weakness
-ment is used to make abstract nouns from verbs: excitement, enjoyment
-hood is used to make abstract nouns, especially family terms, from nouns: childhood, brotherhood
-ship is used to make abstract nouns, especially status, from nouns: friendship, membership, partnership
-(i)ty is used to make abstract nouns from adjectives: honesty, loyalty