The ɵ (Theta-like) symbol in Angular 2+ source code

Question

After deep immersion in Angular 4.3 source code. * I often came across the symbol ɵ. For example, in async pipe source we see the use of the functions ɵisPromise(_) and ɵisObservable(_) . So now I wonder why the Angular team decided to use it? And what does it mean?

Angular developers seem to label methods / modules with ɵ to emphasize that they are some kind of internal objects that should never be imported. But I did not find authoritative evidence.

After some more in-depth research, I found another interesting fact: basically ɵ is a letter in several Latin alphabets (a wiki was included in the Azerbaijani alphabet used between 1922 and 1933), but it resembles the Greek letter θ (Theta). After some searching on Google, I managed to find the mathematical formula (successfully forgotten after finishing) of calculating the Angular speed, where the letter Theta meant the angle. So maybe this is some kind of humor?

Answer 1

So now I wonder why the Angular team decided to use it? And what does that mean?

Yes, it marks the methods as internal / private. Here is a quote from an article that was written by Uri Shaked who received this information from Angular team members:

The first thing you noticed was a lot of obscure method names, starting with the letter ɵ (Greek theta) and then into 3 other English letters (for example, ɵvid). The letter ɵ is used by the Angular team to indicate that some method is private to the structure and should not be called directly by the user, since the API for this method is not guaranteed to remain stable between versions of Angular (in fact, I would say it is almost guaranteed to break )