
Either the reason is predicated on a SERIES
of sub-reasons leading to regression...
The Big Bang Theory Season 2, Episode 1

But they're gonna run
a whole SERIES of tests, so...
Breaking Bad Season 2, Episode 3

and likely to give rise
to a SERIES of revenge killings
Vikings Season 1, Episode 1

Part of his ongoing SERIES,
The Big Bang Theory Season 12, Episode 20

A NETFLIX ORIGINAL SERIES
Money Heist Season 3, Episode 7