Some capital Greek letters such as ∖[CapitalAlpha] look essentially the same as capital English letters. The Wolfram Language, however, treats them as different characters, and in TraditionalForm it uses ∖[CapitalBeta], for example, to denote the built‐in function Beta.
Following common convention, lowercase Greek letters are rendered slightly slanted in the standard fonts provided with the Wolfram System, while capital Greek letters are unslanted. On Greek systems, however, the Wolfram System will render all Greek letters unslanted so that standard Greek fonts can be used.
Almost all Greek letters that do not look similar to English letters are widely used in science and mathematics. The capital xi is rare, though it is used to denote the cascade hyperon particles, the grand canonical partition function, and regular language complexity. The capital upsilon is also rare, though it is used to denote particles, as well as the vernal equinox.
Curly Greek letters are often assumed to have different meanings from their ordinary counterparts. Indeed, in pure mathematics a single formula can sometimes contain both curly and ordinary forms of a particular letter. The curly pi is rare, except in astronomy.
The final sigma is used for sigmas that appear at the ends of words in written Greek; it is not commonly used in technical notation.
The digamma, koppa, stigma, and sampi are archaic Greek letters. These letters provide a convenient extension to the usual set of Greek letters. They are sometimes needed in making correspondences with English letters. The digamma corresponds to an English w, and koppa to an English q. Digamma is occasionally used to denote the digamma function PolyGamma[x].
By using menu items in the notebook front end, you can make changes in the font and style of ordinary text. However, such changes are usually discarded whenever you send input to the Wolfram Language kernel.
Script, gothic, and double‐struck characters are, however, treated as fundamentally different from their ordinary forms. This means that even though a C that is italic or a different size will be considered equivalent to an ordinary C when fed to the kernel, a double‐struck will not.
Different styles and sizes of C are treated as the same by the kernel. But gothic and double‐struck characters are treated as different:
In standard mathematical notation, capital script and gothic letters are sometimes used interchangeably. The double‐struck letters, sometimes called blackboard or openface letters, are conventionally used to denote specific sets. Thus, for example, conventionally denotes the set of complex numbers, and the set of integers.
Dotless i and j are not usually taken to be different in meaning from ordinary i and j; they are simply used when overscripts are being placed on the ordinary characters.
Formal symbols are Protected, so they cannot be accidentally assigned a value.
Trying to modify a formal symbol fails:
This means that expressions depending on formal symbols will not be accidentally modified:
Specific values for formal symbols can be substituted using replacement rules.
Verify that the defining equations hold for cosine:
Formal symbols can be temporarily modified inside a Block because Block clears all definitions associated with a symbol, including Attributes. Table works essentially like Block, thus also allowing temporary changes.
Assign a temporary value to y:
In most situations modifying formal symbols is not necessary. Since in DifferentialRoot formal symbols are used as names for the formal parameters of a function, the function should simply be evaluated for the actual values of arguments.
Evaluating the function substitutes x for x and y for y:
It is possible to define custom typesetting rules for formal symbols.
Use coloring to highlight formal symbols:
The formatting rules were attached to MakeBoxes. Restore the original formatting: