Similar symbol (∼)
∼ means “is similar to”: two figures are similar when they have the same shape, with equal angles, though not necessarily the same size. △ABC ∼ △DEF says one triangle is a scaled copy of the other.
Easily confused with
- Congruent symbol (≅)≅ means “is congruent to”: two figures are congruent when they are the same shape and the same size, so one could be laid exactly on the other. △ABC ≅ △DEF says the two triangles are exact copies.
- Tilde (~)The similarity sign is the tilde operator, not the keyboard tilde.
- Not symbol (¬)The same wavy line is an older sign for “not” in logic.
How to read it
Henry Africk’s Elementary College Geometry (CUNY) defines similar triangles as triangles with equal sets of angles and gives ∼ as the symbol, written, like the congruence sign, with matching vertices in the same order. OpenStax’s Contemporary Mathematics adds what follows from that: the sides of one triangle are proportional to the matching sides of the other, and one figure is the other enlarged or reduced by a scale factor.
Also searched as: ∼, similarity symbol, similar sign, similar triangles, tilde in geometry.
Look-alikes
The mathematical ∼ is Unicode’s TILDE OPERATOR (U+223C), a separate character from the keyboard tilde ~. Unicode lists the many things it can mean: “similar to” is one, beside “varies with (proportional to)”, “difference between” and “not” (in older logic, ∼p is not p). A wavy line over two straight ones, ≅, means congruent.
Read next
- Next in Geometry symbolsPerpendicular symbol (⊥)⊥ means “is perpendicular to”: the two lines meet at a right angle, 90°. AB ⊥ CD says line AB is perpendicular to line CD.
- The same shape in Pyrex and Depression glass patternsButterprint (Pyrex pattern)Butterprint is a Pyrex pattern of a farmer and his wife holding a bushel of crops, among wheat sheaves, roosters and corn. Corning Glass Works printed it on opal glass bowls and casseroles from 1957 to 1968, most often turquoise on white or white on turquoise.
More geometry symbols
The same shape elsewhere
Browse symbols drawn with curves and waves.
Sources
- Elementary College Geometry, 4.2 Similar Triangles, Henry Africk, Elementary College Geometry (CUNY New York City College of Technology, 2021), CUNY Academic Works, via LibreTexts, Similar triangles
- Contemporary Mathematics, 10.3 Triangles, OpenStax (Rice University), Similar triangles
- Earliest Uses of Symbols from Geometry, Jeff Miller, Earliest Uses of Various Mathematical Symbols, MacTutor History of Mathematics, University of St Andrews, Similarity
- A History of Mathematical Notations, Vol. I: Notations in Elementary Mathematics, Florian Cajori (Chicago: Open Court, 1928); full text of the Wellcome Collection copy, Internet Archive, § 372 Signs for similarity and congruence
- Mathematical Operators: Range 2200–22FF (code chart), The Unicode Standard, Version 18.0, Unicode Consortium, Relations, 223C
Researched, edited and approved by Rory Hansen before publishing. Last reviewed October 9, 2026. How we research
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