IPA: /ˈdiːpər/
KK: /dipɚ/
Having a greater distance from the top to the bottom or from the surface to the bottom; more profound or intense than something else.
The lake is much deeper than I expected.
Deeper → It is formed from "deep" (from Old English *deop*, meaning profound or far down) and the comparative suffix "-er" (meaning more). The word "deeper" means more profound or further down than something else.
Think of something that is 'more profound' or 'further down' — 'deep' describes a profound state, and '-er' indicates a comparison.