Using the appropriate vocabulary

has been under discussion in our establishment of recent days. 
My nephew, Middle Cat's son, is a doctor. He has been keeping us informed about Middle Cat's progress. 
After talking to him a couple of days ago the Senior Cat said to me,
"You know, he sounds like a doctor when he talks about her."
Yes, he does. He switches to "professional".
But it goes further than that. If he is talking to me he uses the correct technical terms. When he talks to the Senior Cat he uses a slightly simpler vocabulary and he throws in an explanation here or there.
I don't think he is conscious of doing it. It is almost certainly an unconscious "Aunty Cat knows those words and my grandfather needs to be told like the intelligent relative of a patient".
If he judges people correctly then that is good. It means his communication skills are good.
Yesterday I drew someone a diagram to explain her knitting to her. My drawing skills are almost non-existent so this caused some amusement but it enabled her to understand why she was having a problem. 
There was also a very pleasant man at our knitting guild selling some knitting related woodwork. He had made something the Senior Cat wants to make and I told him this. I explained the problem the Senior Cat was having. My language must have suggested that I know the meanings of "chuck" and "tailstock" because he gave me a technical explanation of how he had solved the problem. Someone else standing next to me was looking bewildered but wanted to know how he had made the items so he explained again in quite different terms. When we moved away she said to me, "He'd be a good teacher." Yes, he probably would be.
Late in the afternoon I went to see a friend who has had a stroke. I had been asked to call in as she was distressed about something and, they said, had been "asking" for me. She can, with difficulty, get a few words out but nobody could work out what the problem was.
It wasn't easy. I had to ask a good many "yes" and "no" type questions. Eventually she was able to tell us that she  had heard the "death notices" read on the Radio for the Print Handicapped newspaper programme. The person who reads parts of the paper for the day only reads the names out and listeners can phone and ask for someone to tell them the details if they have nobody who can help. Of course my friend could not do this and she had heard a familiar name. When we had discovered what she wanted to know someone found a paper and yes, sadly, it was her friend. But now she was sad rather than distressed.
As I left one of the staff thanked me for coming in and said, "I was listening to the way you did it."
I am not nearly as expert as I would like to be but I hope she managed to learn something from listening.
We all use multiple means of communication of course. It is using it appropriately which matters.