Minus Tilde

It marks a relation, and the author’s definition gives its exact meaning.

≂ is not a universal shorthand for approximate equality. MathML, a web format for writing formulas, labels it eqsim and glosses it as “equals, similar”; that phrase is a clue, not a rule every author follows.

A tilde has a separate mathematical history: in his mathematics textbook Clavis Mathematicae, published in 1631, William Oughtred used one to mark the absolute value of a difference—the difference’s size without regard to its sign. This records an older use of one component, not the origin date of the combined sign ≂.

Is ≂ the same as ≈?

No; ≈ is the familiar sign for approximate equality.

In a proof or paper, look for the author’s notation key or nearby definition before assigning an exact meaning to ≂. For a rough numerical estimate, ≈ is the clearer conventional choice.

How do I type minus tilde?

In LaTeX, use \eqsim if your setup defines it.

For HTML, the named character references ≂, ≂, and ≂ all insert this sign. MathML’s eqsim and esim labels point to the same character; these entry names do not decide its mathematical meaning.