The asymptotics tag currently has two tags remapped to it: big-o and asymptotic-complexity. I can imagine the reason landau-notation is not amongst those is to distinguish between questions about asymptotics (in general) and the notation itself (and possibly its definition too); this seems to be what the tag description also hints at:
Questions about asymptotic notations such as Big-O, Omega, etc.
However, is there a good reason landau-notation is not synonymous with big-o-notation (as in, e.g., Wikipedia)? Does big-o-notation merit its own tag? Its description currently reads:
Big O Notation is an informal name of the "O(x)" notation used to describe asymptotic behaviour of functions. It is a special case of landau-notation.
So, is big-o-notation a special case of landau-notation, which, in turn, is a special case of asymptotics? How are they related to the notation tag?