副

prefix: vice-; deputy, secondary; auxiliary, classifier for pairs/sets
副

副 has several distinct senses on the page (adjectival/prefix 'vice-/deputy', a classifier for pairs, and a noun 'duplicate/copy') all under the same reading hu3, so the specific intended sense is uncertain; the prefix/adjectival 'vice-' sense was picked as primary since it heads the related compounds 副作用/副官/副手/副本.