sketchbook vs sketch pad

sketchbook and sketch pad both are nouns.

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

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

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

Other synonyms of sketchbook include sketch block.

sketchbook (noun)	sketch pad (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