using "the thing is"

[Bridget]

What does "the thing is..." mean here? Is it commonly used?

The thing is, I can't really make it this week.

The thing is, she's dating a new guy now.

[Pete]

What does "the thing is..." mean here? Is it commonly used?

The thing is, I can't really make it this week.

The thing is, she's dating a new guy now.
I'm used to hearing this in informal conversations. Typically you have been discussing a particular subject for a while, and a number of different statements have been made. Then someone says, "The thing is, …" to say that the following point is the critical one, the one that overrides all the other facts that have been brought up.

In more formal situations, you would probably use some more precise term than "thing" to make your point.

[SomeOne]

What does "the thing is..." mean here? Is it commonly used?

The thing is, I can't really make it this week.

The thing is, she's dating a new guy now.

May I extend these sentences like this:

The thing I'm talking about is, I can't really make it this week.

or maybe:

What I'm talking about is, she's dating a new guy now.

Correct me if I'm wrong, please. :)

[Pete]

May I extend these sentences like this:

The thing I'm talking about is, I can't really make it this week.

or maybe:

What I'm talking about is, she's dating a new guy now.

Correct me if I'm wrong, please. :)
I can't say it is never used that way, but that's not the way I'm accustomed to hearing it. I really think the meaning is more like, for instance,
- The thing that matters most is that I can't really make it this week.
- What you must keep in mind is that she's dating a new guy now.

[Bridget]

<In more formal situations, you would probably use some more precise term than "thing" to make your point.>

For example?

[Pete]

<In more formal situations, you would probably use some more precise term than "thing" to make your point.>

For example?
- The key idea is that …
- The critical/crucial/overriding fact to consider is that …
- The truly relevant issue seems to be that …

[Bridget]

- The key idea is that …
- The critical/crucial/overriding fact to consider is that …
- The truly relevant issue seems to be that …

So if I want to speak formally, I have to say this, right?

The truly relevant issue seems to be that I can't really make it this week.

The critical/crucial/overriding fact to consider is that she's dating a new guy now.

Somehow, they sound odd.

[Uthman]

I think it means "the matter is" or "the problem is"