In a manner that is able to be achieved or accomplished; feasibly or realistically.
From 'attainable' plus the adverbial suffix '-ly.' This forms an adverb that modifies verbs and adjectives, allowing speakers to describe how something is or can be done in an achievable way.
Few people actually use 'attainably' in everyday speech even though it's perfectly grammatical—we say 'realistically' or 'feasibly' instead, which shows how English speakers gravitate toward common words even when rarer synonyms exist.
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