This morning I met some colleagues from the United States and one of them have my equivalent work position in America. I told her that she is my "opposite number "but she didn't understand and she corrected me saying that the proper statement is the "equivalent position."
The "opposite number" is an expression that i Learnt on a british grammar to indicate a person who hold a position in an organization corresponding to that person in another organization...
Might this expression to be used only in england and not also in America?
Your remarks were entirely appropriate in context. I'm an American and I am very familiar with the expression.
Your co-worker cited a "proper statement" as though some absolute rule applied to generalized terminology.
Do not be discouraged. I would readily use either Equivalent Position or Opposite Number to express precisely the same idea.
Many students show with frequency that they have the same misconception as your Opposite Number. They suppose that some kind of absolutist regulation governs English.
If that were true, we would never hear of something termed "slang" or "Idiomatic Expressions".
Also, depending on the experience of people, there may be or may not be familiarity with certain expressions. For example, a person with close associations with various forms of employment as labor, will probably recognize your phrase immediately. Where as a person who went from High School, to College and on to teach "English" or work in one of the professions, might have no familiarity at all with certain expressions.
I was told something very useful as a child.
"Don't believe anything you hear, and only half of what you see."
Gianluca, I think it would be more appropriate to use this expression, for example, when talking about two people on opposing sides. As an instance, suppose you and I were both footballers (real, not American of course!), you playing for Italy and me for England, and we played in the same position in our respective teams then we would be 'opposite numbers' for each other. Likewise for two politicians in opposing parties who hold the same postions in their parties. In my opinion, simply because two people hold the similar positions in different organisations does not necessarily make them opposite numbers.
In my experience it's not widely used in the US. I've heard it before, but rarely, and I've never used it myself.