That is all extremely fascinating Helen!
I find our cats over the years have quite a wide vocabulary, both in understanding our language and in replying/communicating with us.

I've always had three or four at once (sometimes more!) over many decades. And there has always emerged a 'senior cat', usually the oldest but not always. He has been the dominant one and the most intelligent. This has been Simon, Simpson-Sam, Smokey, in turn, and they have all 'talked' to the other, less dominant cats.

Smokey for example knows the phrase, "Did you want...?" as he realises this means goodies on offer. Also, "What's the matter?" and, "Open the door?" "Mind out!" "Mousies!"(which means anything chaseable, including insects, birds, toys or other invading cats) and sadly, "I'll smack that bottom!" (We never smack them of course, but they know that phrase!)
But the most common and anguished howl from me, which they well understand, is, "Who did that bloody wee wee?" because they're forever having a quick squirt here and there and I hate it. Siamese are terrible wee-ers; I've only ever had neutered males, but they all did it!