At one time, I ‘spoke’ three words (in my own language). Then I found myself out of the dream and so could register the words in the conscious mind. In a few other dreams words were spoken, both to me and by me, but the ‘people’ there, unlike in the first case, were not ones that had impacted on my life, so I remembered what was ‘said’ for only a couple of days.
In by far the majority of cases no words are spoken, only a simple but unmistakable message is transmitted.
* Afterthought: It is also possible that I actually spoke, i.e vocally, while dreaming; as when we tell someone that they were ‘talking in their dreams’. I have no way of telling.