深重 is a formal stative verb meaning 'very grave' or 'extremely serious', used almost exclusively in formal or literary contexts. It typically modifies abstract nouns like 灾难 (disaster), 罪行 (crime), 苦难 (suffering), and 危机 (crisis). Unlike more common words for 'serious' (e.g. 严重), 深重 often implies a sense of moral heaviness or historical significance, and appears in fixed expressions like 罪孽深重 (full of sin) and 灾难深重 (disaster-stricken).