Today, we are looking at some five phrases in which article ‘the’ is a compulsory element, but which is often erroneously left out. The first is associated with phone calls: on the phone. When an ongoing call prevents you from attending to another matter, and you need to state the reason, the standard thing to say is you are/were ‘on the phone’, not on phone:
Sorry, I was on call when you entered. (Wrong)
Sorry, I was on phone when…
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