What does this symbol mean in math ? ~

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Step-by-step explanation:

1.  Between two numbers, either it is used in place of ≈ for meaning "approximatively equal", or it means "has the same order of magnitude as".

2.  Denotes the asymptotic equivalence of two functions or sequences.

3.  Often used for denoting other types of similarity, for example, matrix similarity or similarity of geometric shapes.

4.  Standard notation for an equivalence relation.