disk harrow vs disc harrow

disk harrow and disc harrow both are nouns.

Word	Noun	Adjective	Verb	Adverb
disk harrow	Yes	No	No	No
disc harrow	Yes	No	No	No

As nouns, disk harrow and disc harrow are synonyms defined as:

disk harrow and disc harrow: a harrow with a series of disks set on edge at an angle

disk harrow (noun)	disc harrow (noun)
a harrow with a series of disks set on edge at an angle	a harrow with a series of disks set on edge at an angle