memory vs scratchpad

memory and scratchpad both are nouns.

Word	Noun	Adjective	Verb	Adverb
memory	Yes	No	No	No
scratchpad	Yes	No	No	No

As nouns, scratchpad is a hyponym of memory; that is, scratchpad is a word with a more specific, narrower meaning than memory:

memory: an electronic memory device
scratchpad: (computer science) a high-speed internal memory used for temporary storage of preliminary information

memory (noun)	scratchpad (noun)
an electronic memory device	(computer science) a high-speed internal memory used for temporary storage of preliminary information
the power of retaining and recalling past experience
the cognitive processes whereby past experience is remembered
something that is remembered
the area of cognitive psychology that studies memory processes