The compound 'twice-yearly' is a modern English formation built from native Germanic elements. The quantifying term 'twice', with its origins in Old English words for 'two', is combined with the noun 'year', a fundamental unit of time tracing back to Proto-Indo-European. The suffix '-ly', also of Old English origin, is then appended to convert the phrase into a single adjectival or adverbial unit. This transparent construction follows a straightforward logical pattern: 'two times' + 'per year', resulting in the clear, scheduled meaning of semiannual occurrence.

Structure: twice (two times) + year (period of 365 days) + ly (adjective/adverb suffix) - twice: From Old English twīwa, twīga ('two times'), related to twā ('two'). It functions as a quantifying element. - year: From Old English gēar ('year'), from Proto-Germanic jērą. It functions as the noun base specifying the period. - ly: From Old English -līc (adjective-forming suffix) and -līce (adverb-forming suffix). It functions as a suffix to form adjectives and adverbs.