Neatly splicing two threads, a reader offers this:

“Here’s a definition of inflection point that might be more helpful to your

readers: The inflection point is the spot where a thing (political issue,

movement, campaign, etc.) stops increasing its momentum and starts

decreasing its momentum (or vice versa). It is still moving in the same

direction (so it hasn’t turned), but it now looks like it will eventually

stop, rather than continue indefinitely.

“Gay marriage is a political (rather judicial) movement that kept increasing

its momentum with every court case that was filled. The Goodridge decision

was an inflection point (not a turning point) in that it spurred the

Conservative opposition to move on a Constitutional amendment. Gay marriage

is still progressing (going forward) in its judicial implementation

strategy, but it is definitely losing momentum at the present point and may

very well grind to a complete stop.

“For a bunch of conservatives ’standing athwart history yelling, “Stop!”’

the inflection point is a necessary first step in defeating foolhardy

attempts to change the status quo.”

And all without a single diagram!

[Note that since momentum is just mass times velocity, and

acceleration/deceleration are just increasing/decreasing velocity, and

therefore momentum, this is really the same as the non-mathematical

definition I gave — if you ignore relativistic effects…]