Natural selection
Etymology
Coined by Charles Darwin in 1859, deliberately echoing the “artificial selection” by which breeders shape livestock — nature, he argued, does the choosing instead of a farmer, over vastly longer time.
noun phrase · /NATCH-er-ul seh-LEK-shun/
The process by which traits that help survival and reproduction become more common over generations, because their bearers leave more offspring.
What it names
How design can arise without a designer: no intention, just the automatic accumulation of whatever happens to work slightly better.
Example
On the peppered moth, natural selection favored dark wings when soot blackened the trees, then pale wings again once the air cleared.
Related idea
Natural selection is the mechanism; evolution is the result it produces. Selection needs mutation to supply the variety it acts on — without new variants, there is nothing to select between.