Depreciate is most common in financial contexts, where it means to lessen the price or value of. It also means to lessen something’s value by derision or criticism or to disparage. Deprecate originally meant to express disapproval of. But deprecate has encroached on depreciate’s second sense so thoroughly that we must accept that the two words are synonyms in that sense.
The phrase self-deprecating, meaning undervaluing oneself, makes less sense than self-depreciating, yet self-deprecating is far more common, and some readers might consider self-depreciating an error.
Examples
The most straightforward application of these words is in financial and monetary contexts, where depreciate is appropriate and usually used correctly—for example:
Vehicles with high retained value in their early years, he says, usually last longer than vehicles which depreciate more quickly. [Globe and Mail]
The good news for U.S. farmers is that the dollar will continue to depreciate against most currencies over the next few years. [Southwest Farm Press]
Deprecate is occasionally used in its original sense, meaning to express disapproval—for example:
I deprecate Bill Aitkens’ reported comments, which were rightly greeted with outrage from both general public and across the political spectrum. [quoted in New Statesman]
From this perspective, to deprecate multiculturalism is to deprecate tolerance. [Independent]
But, mostly, deprecate is used interchangeably with depreciate, meaning to lessen something’s value:
I do not mean to deprecate the importance of air and naval power, which matter greatly. [Frum Forum]
Microsoft exerted control over developers by requiring changes to boot-up screens and deprecating Netscape’s ability to compete in browsers. [The Register]
And although self-depreciating usually makes more sense than self-deprecating, the latter appears about 40 times as often. For example, these major publications use self-deprecating:
First, being self-deprecating always, always works. [Los Angeles Times]
Self-deprecating irony has always balanced the brimstone, and the beard that looks like a prophet’s may just be because he’s Texan. [Independent]
Gadsby’s humour is a phlegmatic mix of dry observation and self-deprecating storytelling. [Sydney Morning Herald]
It’s always unfortunate when we lose the original meaning of a useful word like deprecating, but this change is now so engrained in the language that it probably can’t be reversed.
