Why are these different?
- We heard the news on the radio.
- We watched the news on television.
In this book, the author says we must use television without the. Why? It makes me crazy. Is there a valid reason?
These are my assumptions based on the the Longman Dictionary entry for 'television'and the examples cited there. According to this entry,
The word television can refer to a) the equipment as well as b) the programmes broadcast on television.
From the examples cites there, I understand that we use the definite article when we are referring to the device.
On the other hand, it looks like we can omit the definite article if we are referring to the programmes.
The third entry on the dictionary is:
on (the) television:broadcast or being broadcast on television:
Probably, in this type of usage with the preposition, it is fine to omit or use the definite article.
I have thought about this for a long time, but I am afraid I can think of no reason why it is as it is. This is just idiom; you need to learn it without any overarching rule, alas.
There are several ways in English to denote that you are talking about something in general rather than a specific instance:
In some cases you could use several ways; not all are possible in each case.
The author has a big ego.
There is certainly nothing wrong with "we watched the news on the television" neither in usage nor in grammar.
There is a huge volume of ridiculous advice out there by experts who should know better.