I'm working on a translation of a paper in portuguese to english. In this paper I work with the average of parameter, but I'm not sure if I should use the word 'average' or 'mean' (specially on graphics). For a non native it's the same thing, but I do not know what word is more scientifically accepted.
Technically speaking, average is colloquial (i.e. which average do you mean? See this Wikipedia page on different averages).
To refer to what is normally referred to as average (i.e. the sum of n terms divided by n) use: Arithmetic mean.