Uncial is a majuscule script, written entirely in capital letters, was commonly used from the 4th to 8th centuries AD by Latin and Greek scribes. Uncial letters were used to write Greek, Latin, and Gothic.
Early uncial script is likely to have developed from late Old Roman cursive. Early forms are characterized by broad single stroke letters using simple round forms taking advantage of the new parchment and vellum surfaces, as opposed to the angular, multiple stroke letters, which are more suited for rougher surfaces, such as papyrus. In the oldest examples of uncial, such as the De bellis macedonicis manuscript in the British Library, all of the letters are disconnected from one another, and word separation is typically not used. Word separation, however, is characteristic of later uncial usage.
As the script evolved over the centuries, the characters became more complex. Specifically, around AD 600, flourishes and exaggerations of the basic strokes began to appear in more manuscripts. Ascenders and descenders were the first major alterations, followed by twists of the tool in the basic stroke and overlapping. By the time the more compact minuscule scripts arose circa AD 800, some of the evolved uncial styles formed the basis for these simplified, smaller scripts. Uncial was still used, particularly for copies of the Bible, tapering off until around the 10th century. There are over 500 surviving copies of uncial script, by far the largest number prior to the Carolingian Renaissance.
The term half-uncial or semi-uncial was first deployed by Scipione Maffei, Istoria diplomatica (Mantua, 1727); he used it to distinguish what seemed like a cut-down version of uncial in the famous Codex Basilicanus of Hilary, which contains sections in each of the two types of script. The terminology was continued in the mid-18th century by René Prosper Tassin and Charles François Toustain. Despite the common and well-fixed usage, half-uncial is a poor name to the extent that it suggests some organic debt to regular uncial, though both types share features inherited from their ancient source. See now: L. E. Boyle, "'Basilicanus' of Hilary Revisited," in Integral Palaeography, with an introduction by F. Troncarelli.
Like uncial, half-uncial derived from Roman cursive, but now of a later, evolved type. It was first used around the 3rd century and remained in use until the end of the 8th century. The early forms of half-uncial were used for pagan authors and Roman legal writing, while in the 6th century the script came to be used in Africa and Europe (but not as often in insular centres) to transcribe Christian texts.