A telephone is the actual physycal machin

[moseen]

Hello all!
In the reference below, why is it said "A telephone is the actual physical machine", cant we say" A telephone is an actual physical machine"?
I have the same question about: "the telephone is the system of communication".
Reference: http://advice.writing.utoronto.ca/wp-content/uploads/sites/2/definite-article.pdf.

 

[teechar]

Hello all!
In the reference below, why [STRIKE]is[/STRIKE] does it say [STRIKE]said[/STRIKE] "A telephone is the actual physical machine"? Cant we say" A telephone is an actual physical machine"?

"A telephone is the actual physical machine that we use for talking to each other over a distance."
I inserted the words in blue to illustrate that we are talking about a specific type of machine.

Yes, you can say "A telephone is an actual physical machine", for example, to define/describe a telephone.

I have the same question about: "the telephone is the system of communication".

The orange "the" is explained in that reference (used with systems of communication), and the green one is because we are talking about a specific system (of communication).