When discussing between people, many assumptions are made. It is important to make those assumptions explicit.
For example, let us take a house. Can you picture it? Yes? How do you know that you are picturing the same house as me?
Let me describe you the house I was imagining and you tell me if it was the same:
My house had the following:
You see the point! At this stage, I am pretty sure that at least one requirement from my house mismatched what you were thinking (or maybe, you had not even thought about it).
Whenever this happens it is important to make it explicitly.
As a French author Bernard Werber said:
Entre ce que je pense, ce que je veux dire, ce que je crois dire, ce que je dis, ce que vous avez envie d’entendre, ce que vous croyez entendre ce que vous entendez, ce que vous avez envie de comprendre, ce que vous croyez comprendre, ce que vous comprenez, il y a dix possibilités qu’on ait des difficultés à communiquer. Mais essayons quand même…
Which roughly translates to
Between what I think, what I want to say, what I believe I say, what I say, what you want to hear, what you believe to hear, what you hear, what you want to understand, what you think you understand, what you understand…They are ten possibilities that we might have some problem communicating. But let’s try anyway…
When defining a problem, defining requirements, it is extremely important to be explicit about everything.