Usage notes

• The Unicode character U+03D5 GREEK PHI SYMBOL (ϕ) was intended for the mathematical symbol. It is not used at all for written Greek; instead, U+03C6 GREEK SMALL LETTER PHI (φ) should be used.^[1] Capitalization, for example, only works for the latter.
• The Unicode 3.0 standard (2002) states: "Fonts used primarily for Greek text may use either glyph form for U+03C6, but fonts that also intend to support technical use of the Greek letters should use the loopy form to ensure appropriate contrast with the straight form used for U+03D5."^[1] However, prior to Unicode 3.0 the glyphs on the Unicode chart were reversed, so that the alphabetic letter U+03C6 GREEK SMALL LETTER PHI (φ) was straight and the mathematical symbol U+03D5 GREEK PHI SYMBOL (ϕ) had a loop, and many fonts developed prior to 2002 copied the reversed glyph shapes.^[1] Independently of this, may write the golden ratio with either ${\displaystyle \phi }$ (\phi or ${\displaystyle \varphi }$ (\varphi) in LaTeX) .