How should we define "teacher", now and future?

Yes, I am the same guy who asked how TOEFL works, Being the abominable monster of whatever I think I am I am, I simply went off defining teachers as anything that can teach(which includes Khan Academy the website, the Iphone, the Youtube App, etc) and got away with it because they only care about examples.

...

So, the justification for that is that if you insert a brain chip intended to enhance memory and essentially making a teacher more machine and less man mentally, it should still be considered as a teacher. If you chop the teacher's limb off, even put it into black armor or something, even going far enough that all "humanly" traits are gone and download the memory into a computer which retains all the memory and can display all of them freely, it would make no difference as that should still be a teacher. But after half-assing a proof, here is a question: does a teacher require sentience to be a teacher?

And let us not deny that websites and non-sentient objects like phones or even toasters can teach you stuff, regardless of them not being solely created to be teachers. Does a subject have to be specialized in teaching to be a teacher?

And I haven't started on part-time teachers working multiple jobs. I intend to apply the second question above to this group. How about scientists who just happen to lecture people because they are too good at their field and nobody else can teach it as good as them. Scientists are more bound to investigate the world than to teach it. In fact, any street cleaner paid minimum wage can teach me how to operate their sweeping vehicle on the street and any pianist can just teach me tunes, as long as they are willing. Is "Teacher" the title of a specific job or not, and are they a job that can be held by anyone? If not, what is the distinctive phrase describing what I have just described here?

If I open an informative site and left with considerably more knowledge than I had before, what is the teacher? Is it the site itself, or the writer of the webpages?

A teacher is a person that teaches, especially in a school...But not exclusively in a school.

If you acquire knowledge from a website, then you have self taught.

The site and the writers simply provide you with the relevant data.

Wait till you hear about one of my teachers who majorly just assigns representative problems to solve on the textbook, and we actually learned how to do it. Less effective variations to this kind also exist. Web programmers and writers are as qualified to be a teacher as an actual teacher, with the only difference being that it isn't exactly institutionalized or categorized as a "school".

Well, the older you get, the more education becomes about research and self motivation.

Younger pupils require motivation and instruction.

Teachers are there to maintain order and application.

Ultimately, teachers are just as reliant upon documented knowledge as everyone else is.

And anyone could be an effective teacher, if they applied themselves appropriately.

Hypothetically, a programmer just jammed rogue code and made it run. The code, nowhere sentient, spewed out a web page that is in fact very educational. Who is the teacher here? The program, the site, or the programmer?

Well the programmer programs data into the site, the site is the holder and provider of such data and the teacher encourages you to input, store and repurpose said data.

And like I said...... As pupils  get older, they are encouraged to be more self motivated and less reliant on direct instruction.

Because when you leave school you will be expected to think for yourself.

A teacher’s prime function is to ensure that learning is taking place.

I suppose some people might say their teachers were nature, or the streets, or Sesame Street,

Still that's the same word with different 'meanings though,

Teacher's more often specifically meant for an instructor, I think.