An alternate is a variant shape of a character, which has to be considered as a glyph of its own.

Alternate glyphs are created for various reasons:
• contextual: such as case-sensitive punctuations, where punctuation symbols can be aligned in a nicer way with capital letters when set within them, or tabular figures if they are used in numeric tables;
• positional: in Arabic or other scripts that have connected characters, a character may need to have different shapes depending on its position in a word (initial, medial, final, isolated);
• stylistic: such as single-story or double-story letters a or g. These alternates can also reflect a specific aesthetic choice (e.g., with or without swashes).
• localization: some languages using a same script as others require a different form of the same character as localized preference variant.

In digital fonts, these variants are accessed through OpenType features. Each one is tagged with a specific code (added as an extension to a glyph’s name) that enables a software to apply them whenever needed. Some most used ones being listed below:
• .calt: contextual alternates;
• .case: case-sensitive forms
• .ss01, .ss02, etc.: stylistic sets;
• .locl: localized forms;
• .onum: oldstyle figures;
• .tnum: tabular figures