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Uppercase, capital, or large letter in calligraphy, in contrast to the minuscule, lowercase, or small letter. All the letters in a majuscule script are contained between a single pair of real or theoretical horizontal lines. The earliest known Roman majuscule letters are in the style known as square capitals, distinguished by downstrokes that are heavier than upstrokes and by serifs (short strokes at right angles to the top and bottom of a letter). Square capitals were used mainly in inscriptions on Roman imperial monuments. Rustic capitals, used in books and official documents, formed a freer, more elliptical script. Roman cursive capitals, a running-hand script used for notes and letters, were a forerunner of the minuscule scripts that appeared later.

Learn more about majuscule with a free trial on Britannica.com.

Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.

Phi (uppercase Φ, lowercase φ or ϕ), pronounced [fī] in modern Greek and as [faɪ] in English, is the 21st letter of the Greek alphabet. In modern Greek, it represents [f], a voiceless labiodental fricative. In Ancient Greek it represented [pʰ], an aspirated voiceless bilabial plosive (from which English ultimately inherits the spelling "ph" in words derived from Greek). In the system of Greek numerals it has a value of 500 (φʹ) or 500,000 (͵φ).

The lower-case letter $varphi\; ,$ (or often its variant, $phi\; ,$) is used as a symbol for:

- The golden ratio 1.618... in mathematics, art, and architecture.
- Euler's totient function φ(n) in number theory; also called Euler's phi function.
- The probability density function of the normal distribution in mathematics and statistics.
- An angle, typically the second angle mentioned, after θ (theta). Especially:
- The argument of a complex number.
- The phase of a wave in signal processing.
- In spherical coordinates, mathematicians usually refer to phi as the polar angle (from the z-axis). The convention in physics is to use phi as the azimuthal angle (from the x-axis).
- One of the dihedral angles in the backbones of proteins.
- Internal or effective angle of friction
- Electric potential in physics.
- The work function in electronics.
- A shorthand representation for an aromatic functional group in organic chemistry
- The fugacity coefficient in thermodynamics
- The ratio of free energy destabilizations of protein mutants in phi value analysis
- In cartography and navigation, latitude.
- A sentence in first-order logic.
- Porosity in geology.

The upper-case letter Φ is used as a symbol for:

- The golden ratio conjugate 0.618... in mathematics.
- The magnetic flux and electric flux in physics, with subscripts distinguishing the two.
- The cumulative distribution function of the normal distribution in mathematics and statistics.
- Philosophy.
- Strength (or resistance) reduction factor in structural engineering, used to account for statistical variabilities in materials and construction methods.
- The number of phases in a power system in electrical engineering, for example 1Φ for single phase, 3Φ for three phase.
- The symbol of the voiceless bilabial fricative in the international phonetic alphabet.

The diameter symbol in engineering, ⌀, is often incorrectly referred to as "phi". This symbol is used to indicate the diameter of a circular section, for example ⌀14 means the diameter of the circle is 14 units.

- upper case:
- U+03A6 GREEK CAPITAL LETTER PHI (Φ): Greek capital letter phi
- lower case:
- GREEK SMALL LETTER PHI (φ): letter phi, used in Greek texts.
- U+03D5 GREEK PHI SYMBOL (ϕ): phi symbol, for mathematical and technical contexts.

In HTML/XHTML, the upper and lower case phi character entity references are `Φ` (Φ) and `φ` (φ) respectively.

In LaTeX, the math symbols are `Phi` ($Phi,!$), `phi` ($phi\; ,!$), and `varphi` ($varphi,!$).

In some browsers (e.g. Internet Explorer 6), the shapes of the U+03C6 GREEK SMALL LETTER PHI (which should be viewed as a curl) and U+03D5 GREEK PHI SYMBOL (which should be viewed as a circle crossed by a slash) are exchanged. Compare these samples to check your browser:

- Phi letter: right $varphi,!$; possible wrong φ

- Phi symbol: right $phi,!$; possible wrong ϕ

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Last updated on Wednesday October 08, 2008 at 05:39:21 PDT (GMT -0700)

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This article is licensed under the GNU Free Documentation License.

Last updated on Wednesday October 08, 2008 at 05:39:21 PDT (GMT -0700)

View this article at Wikipedia.org - Edit this article at Wikipedia.org - Donate to the Wikimedia Foundation

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