In a way that is on or relates to the outside surface or outer part of something.
From exterior + -ly (Old English -lice 'in the manner of'). The adverbial suffix -ly transforms the adjective exterior into an adverb describing how something happens or appears.
While 'externally' focuses on what's outside versus inside a system, 'exteriorly' specifically emphasizes the outer surface itself—it's the word for the purely visual, surface-level aspect.
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