Discussion Groups / English Usage / January 2010

On 27 Jan 2010, mm wrote

Nor to me.

Other dictionaries of idioms appear too disagree with that one:
(from http://idioms.thefreedictionary.com/by+definition)

(quote)

by definition - because of the nature of someone or something
_Circus performers are, by definition, delightful show-offs and
risk takers_.

Cambridge Dictionary of American Idioms Copyright © Cambridge
University Press 2006. Reproduced with permission.

(/quote)

That sort of example could fit the usual meaning of "by definition" in a
particular context. Imagining a context:

"Researchers have discovered a new class of antibiotics which work in a
different way from those currently in use. Antibiotics of this new type
are more effective than existing types. XYZ is the first of this new
type to be marketed. This antibiotic is by definition the most effective
now on the market."

However, using an example in a dictionary without even hinting at the
"definition" is silly.

I know the phrase from mathematics and engineering. For example, you
might say that variable R has a direction by definition, because
earlier you've defined it as a vector. Or you might say that a
particular object is subject to corrosion by definition, because
you've earlier said it's made of plain carbon steel.

If there hasn't been an earlier definition, at least an implied one,
then that phrase hasn't been used properly. The examples cited in
this thread aren't, in my opinion, proper uses, but there's nothing
to be done about it.