All 6 Uses of

phenomenon
in
Freakonomics

Now only two things were needed to turn crack into a phenomenon: an abundant supply of raw cocaine and a way to get the new product to a mass market.†
p. 108.2

phenomenon = something that exists or happened -- often of special interest

While crack use was hardly a black-only phenomenon, it hit black neighborhoods much harder than most.†
p. 111.9 *

We have evolved with a tendency to link causality to things we can touch or feel, not to some distant or difficult phenomenon.†
p. 140.4

Many theories have been put forth over the years: poverty, genetic makeup, the "summer setback" phenomenon (blacks are thought to lose more ground than whites when school is out of session), racial bias in testing or in teachers' perceptions, and a black backlash against "acting white."†
p. 161.6

Roland G. Fryer Jr., the young black economist who analyzed the "acting white" phenomenon and the black-white test score gap, may be among the next.†
p. 184.2

Definitions:

(1) (phenomenon)
something that exists or happened -- especially something of special interest -- sometimes someone or something that is extraordinary

"Phenomenons" and "phenomena" are both appropriate plural forms of this noun. "Phenomena" is generally used in scientific or philosophical contexts.
(2) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

In philosophy, a phenomenon is something as known through the senses. It is contrasted with a noumenon.