极 (jí) means 'extremely' and is more formal and intense than 非常 (fēicháng) and 太 (tài). Unlike 太, which often implies excess or subjective judgment (especially in 太…了), 极 is a neutral, strong intensifier used in both spoken and written Chinese. It can also appear as a complement (好极了), but as an adverb it directly precedes the adjective or verb.