thingˈness noun

1. The character or fact of being a thing
2. Reality

thingˈy adjective

1. Real
2. Actual
3. Objective
4. Matter-of-fact

Thingumajig

thing-in-itselfˈ noun

(in the philosophy of Kant) a noumenon, the German Ding an sich

a good thing

A fortunate circumstance

and things

And other (similar) things

a stupid (or wise, etc) thing to do

A stupid (or wise, etc) action

be all things to all men

1. To meet each person on his or her own ground, accommodate oneself to his or her circumstances and outlook (Bible, 1 Corinthians 9.22)
2. (loosely and disparagingly) to keep changing one's opinions, etc, so as to suit one's company

be on to a good thing (informal)

To be in a particularly profitable position, job, etc

do one's (own) thing (informal)

1. To behave as is natural to or characteristic of oneself
2. To do something in which one specializes

do the handsome thing by

To treat generously

do things to

To affect in some good or bad way

for one thing … for another (thing)

Expressions used in enumerating reasons

have a good thing going (informal)

To be established in a particularly profitable position, etc

hear things

To hear imaginary noises, voices, etc

know a thing or two (informal)

To be shrewd

make a good thing of it

To reap a good advantage from

make a thing of

1. To make an issue, point of controversy, etc of
2. To fuss about

no such thing

1. Something very different
2. No, not at all

not a thing (informal)

Nothing

not quite the thing (old informal)

Not in very good health (see also the thing below)

(now) there's a thing (informal)

That surprises me

one of those things

A happening one cannot account for or do anything to prevent

see things

To see something that is not really there

the thing or the done thing

That which is conventional, fashionable, approved, right or desirable