sustain vs keep on

sustain and keep on both are verbs.

Word	Noun	Adjective	Verb	Adverb
sustain	No	No	Yes	No
keep on	No	No	Yes	No

As verbs, keep on is a hyponym of sustain; that is, keep on is a word with a more specific, narrower meaning than sustain:

sustain: lengthen or extend in duration or space
keep on: allow to remain in a place or position or maintain a property or feature

Other hyponyms of sustain include continue, keep, retain.

sustain (verb)	keep on (verb)
undergo (as of injuries and illnesses)	allow to remain in a place or position or maintain a property or feature
establish or strengthen as with new evidence or facts
admit as valid
supply with necessities and support
provide with nourishment
be the physical support of; carry the weight of
lengthen or extend in duration or space