I will say Doug, that from the beginning, my wife and I were on the same page in being consistent with words and phrases we used. Consistency is key for them to understand what you are describing as a material item or an action. An example would be when we give him a food item or prepare a mixture. Each item is described like Apple, Grape, Carrot, Chicken etc or Turn the light on, Turn the Light Off, Turn the TV on etc. I think this fairly well describes how we have interacted with him from day one.
He knows and says everything at it's correct time based on either what he wants, what he is doing or what he observes happening in real-time. First thing he says in the morning is "Turn the Light On", meaning the light over his cage, then Take the Cover off... as an example. He knows the correct human description for everything that occurs in a normal day. His vocabulary at this point is over 500 words/phrases.