Question

Short note on derivational suffixes

Answer 1

When the word is changed from one class to another it is known as a Derivational suffix and by adding few words, in the end, changes the words or makes the new word. 
For example, wash, if we add 'able', a new word will be produced. Which is washable.

Answer 2

A derivational suffix is a morpheme or words added at the end of the word to form a new word or change the meaning of the word.

Example, with the suffix -etic (means relating to), an athlete is changed into athletic and energy is changed into energetic which changes the meaning of the word.