selection vs survival of the fittest

selection and survival of the fittest both are nouns.

Word	Noun	Adjective	Verb	Adverb
selection	Yes	No	No	No
survival of the fittest	Yes	No	No	No

As nouns, selection and survival of the fittest are synonyms defined as:

selection and survival of the fittest: a natural process resulting in the evolution of organisms best adapted to the environment

Other synonyms of selection include natural selection, survival.

selection (noun)	survival of the fittest (noun)
the act of choosing or selecting	a natural process resulting in the evolution of organisms best adapted to the environment
the person or thing chosen or selected
a passage selected from a larger work
an assortment of things from which a choice can be made
a natural process resulting in the evolution of organisms best adapted to the environment