compound adjectival word-forming element, usually interchangeable with -ic but sometimes with specialized sense (such as historic/historical, politic/political), Middle English, from Late Latin -icalis, from Latin -icus + -alis (see -al (1)). Probably it was needed because the forms in -ic often took on a noun sense (for example physic). Forms in -ical tend to be attested earlier in English than their twins in -ic.
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Definitions of hierarchical
classified according to various criteria into successive levels or layers;
in her hierarchical set of values honesty comes first
it has been said that only a hierarchical society with a leisure class at the top can produce works of art