sketch pad vs sketchbook

sketch pad and sketchbook both are nouns.

Word	Noun	Adjective	Verb	Adverb
sketch pad	Yes	No	No	No
sketchbook	Yes	No	No	No

As nouns, sketch pad and sketchbook are synonyms defined as:

sketch pad and sketchbook: a book containing sheets of paper on which sketches can be drawn

Other synonyms of sketch pad include sketch block.

sketch pad (noun)	sketchbook (noun)
a book containing sheets of paper on which sketches can be drawn	a book containing sheets of paper on which sketches can be drawn