Phase Symbol φ

Phase Symbol uses the Greek small letter phi, φ, encoded as U+03C6 GREEK SMALL LETTER PHI. On this page, φ is treated specifically as a phase variable in physics and engineering—not as a general discussion of the Greek letter. The equation or diagram must define what the phase is measured against and whether the value is expressed in radians or degrees. Typical forms include x(t) = A cos(ωt + φ), Phase difference: Δφ, φ = 90°, and Complex phase: e^{iφ}. These examples place φ inside wave equations, AC circuit analysis, signal processing, and optics. A bare φ without a reference signal or definition is incomplete because phase is normally relative to another waveform, origin, or coordinate convention. Both pages use the same encoded character U+03C6, but their purposes differ. This page documents φ as a technical variable for phase. It does not claim that φ always means phase, and it does not replace a general Greek-letter reference page. In mixed technical documents, define “φ = phase angle” before the first equation. Common mistakes include switching between degrees and radians without a label, treating uppercase Φ and lowercase φ as interchangeable, omitting the reference used for a phase difference, and confusing phase φ with frequency f or angular frequency ω. Keep the complete equation visible so readers can tell which quantity the variable represents. For formatting, retain lowercase φ, identify the unit convention, and use equation markup when exponents, fractions, or complex expressions are involved. A readable phrase such as “phase phi” is useful when the glyph appears in an accessible label. On Windows, Microsoft Word can convert 03C6 with Alt+X; other applications may require Character Map or copy and paste. On macOS, Character Viewer can locate “Greek small letter phi.” After insertion, verify that the result is lowercase φ and that the surrounding equation still defines its phase role.