Richard Wordingham <[email protected]> wrote: > U+0278 LATIN SMALL LETTER PHI is for IPA usage, and, unlike Greek, > always has an ascender.
For linguistic Greek usage, the two variants are considered equivalent. This is not the case in Maths where thee two variants are clearly distinct. That's why (La)TeX preserves a distinction between \phi (with an ascender, in fact drawn with a separate stroke on top of a circle, also typically used in linguistic Greek for non cursive style of books) and \varphi (without the ascender, in fact wholy drawn with a single self-intersecting curved stroke, also typically used in linguistic Greek, for more cursive styles, either handwritten, or in books — even in monospaced fonts — for italic styles). Note that both variants are existing in roman/straight and italic/slanted styles. You'll immediately see that the variant with the ascender is not favored in linguistic uses for the italic style, because it becomes too much near from a slashed lowercase Greek omicron (or Latin/Cyrilic o). You will also easily confuse it with the notation for an empty set, so the \phi variant of LaTeX is most often avoided in most formulas, in favor of \varphi (unless there's a real need to use both distinctly in the same article text). But these \phi and \varphi variants are generally not distinct, except (once again) in some mathematical formulas that need a rich set of variables, or need a convention to make distinction between operands and operators, or between scalars, vectors, tensors, torsors, fields, differentiators and so on (or between variables belonging to distinct definition domains, or in dual sets) : the same reasons explain why there are other similar distinctions as well for all basic Latin letters (and digits, as well as Hebrew letters) between italic, bold, serif, sans-serif, and monospaced styles, with additional codepoints defined as symbols rather than letters, preserving the needed semantic distinctions in formulas, but not needed for normal linguistic orthographies which should always avoid these symbols. -- Philippe.
