Plural form; multiple instances or areas of things lying around or surrounding something.
From Latin 'circum' (around) + 'jacencies' (plural of jacency, from 'jacere' to lie). The plural form reflects situations where multiple surrounding regions or surrounding objects need to be referenced simultaneously.
This wonderfully cumbersome plural appears in old regional descriptions—imagine a medieval monk writing about all the circumjacencies of Rome, meaning all the territories encircling the papal city! Modern writers would just say 'surrounding areas,' but the specificity of this word shows how precisely Renaissance scholars described geography.
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