All three of these verbs may be used with countable or uncountable nouns when the intended meaning is “to lessen” or “to become smaller.” Deciding which to choose depends upon context and the connotation wanted.

Diminish descends from a Latin verb meaning “to cut small. Ancient Latin had the verb diminuere, “to break into small pieces, and diminuere, “to make smaller, to reduce in size.”

Decline derives from Latin declinare, “to turn or bend away or aside from the straight course.”

Dwindle derives from dwine, an archaic English verb meaning, “to waste or pine away.”

That all three are used interchangeably in modern English is illustrated by the following examples from the Web:

As populations age and revenues diminish, government and private pension funds around the world are facing insolvency.

Nevada and Strip gaming revenues decline in February

Chicago food fest struggles as revenues dwindle

Diminish conveys a lessening of the strength or quality of something. Its most common use is with uncountable nouns:

Are we getting more stupid? Researchers claim our intelligence is diminishing as we no longer need it to survive

Researchers have some new insights into how power diminishes a person’s capacity for empathy.

Our smartphones supply endless possibilities for entertainment, but a new study shows they can diminish the quality of users’ time away from work or school.

Decline connotes a gradual diminishing, like something moving down a slope.

We had watched our children decline, fall into drug and alcohol abuse, fail to perform at school, lose jobs, abandon relationships, become unable to function in the family or society, and we hadn’t known why.

Agriculture is declining day by day.

The six months…had been for me a sorrowful waiting game of watching [my mother] decline and wondering which day would be her last.

Dwindle suggests a gradual diminution into nothingness or something close to it. A novel’s plot might dwindle to a disappointing close. A dying battery causes a flashlight’s illumination to dwindle. The liquid in the “Drink Me” vial causes Alice to dwindle in size.

An excellent photographic visualization of dwindling is what the Wicked Witch of the West does when Dorothy throws water on her in The Wizard of Oz.

A quotation that I associate with the word dwindle is the line that concludes Millamant’s monologue to her fiancé Mirabell in Congreve’s Way of the World. After listing the freedoms she enjoyed as an unmarried woman as conditions (articles) that he must agree to if he wants her to go through with the marriage, she concludes with this statement:

Credit: DWT

Educating....