I have been wondering for a long time whether there is a unequivocal way to define and use the symbols commonly adopted for an approximate equality between two quantities. I am a physicist, and I often see them used interchangeably and more or less only accordingly to the taste of the author or lecturer.
But what is a reasonable and clear way to differentiate between these symbols?
I refer to:
$$\approx\ \simeq\ \sim\ $$