ideality comes from ideal + -ity, denoting the quality of being ideal, ultimately from Ancient Greek idea ('form, pattern'). Morphologically, the ending is part of the etymology: the suffix is attached to the older base named in the history, producing a later English derivative. In present English, the noun sense is "the quality of being ideal or existing only in imagination", so the historical development ends in a clearly identifiable modern dictionary use. The same base also appears in related forms such as ideal, idealism, idealize, and idea. Its semantic neighborhood includes perfection, idealness, and imaginariness, which helps locate the modern sense without adding a separate etymological claim. The named historical forms include Ancient Greek idea.