safety bike vs bike

safety bike and bike both are nouns.

Word	Noun	Adjective	Verb	Adverb
safety bike	Yes	No	No	No
bike	Yes	No	Yes	No

As nouns, bike is a hypernym of safety bike; that is, bike is a word with a broader meaning than safety bike:

safety bike: bicycle that has two wheels of equal size; pedals are connected to the rear wheel by a multiplying gear
bike: a wheeled vehicle that has two wheels and is moved by foot pedals

Other hypernyms of safety bike include bicycle, cycle, wheel.

safety bike (noun)	bike (noun)
bicycle that has two wheels of equal size; pedals are connected to the rear wheel by a multiplying gear	a wheeled vehicle that has two wheels and is moved by foot pedals
	a motor vehicle with two wheels and a strong frame

safety bike (verb)	bike (verb)
	ride a bicycle