Deference (N): submission to another’s will; respect; courtesy

Dean showed deference to his grandfather.

Definitive (adj) Conclusive; providing the last word

Walter wrote the definitive biography of Keats; nothing more could been added by another book

Degenerate (V): to break down; to deteriorate

The discussion quickly degenerated into an argument.

Deleterious (adj): harmful

Smoking cigarettes is deleterious to your health.

Delineate (V) to describe accurately; to draw in outline

Delude (V): to deceive

She is so persuasive that she was able to delude her friends into thinking she was a countless.

Delusion (N)

Deluge (N): a flood; an inundation

A deluge is a flood, but the word is often used figuratively.

Demagogue (N): a leader who uses prejudice to get more power

Demagogues manipulate the public to support their aims, but they are little different form dictators.

Denizen (N): inhabitant

Fish are sometimes referred to as ‘denizens of the deep.’ Do not refer to them this way yourself; the expression is a cliché.

Depravity (n): extreme wickedness or moral corruption, immorality, 

 

Deprecate (v) to express disapproval of

It is a deprecating remark 

Deride (V): to ridicule; to laugh at contemptuously

The boss derided her secretary mercilessly, so he quit his job. He was someone who could not accept derision.