assistant, associate, vice-...

to meet (wishes, expectations, etc.)...

adverb

to garnish, to accompany (as a card does a gift), to add to as support...

side effect, adverse reaction

executive vice-president

vice-governor, deputy governor, lieutenant governor

supplementary prize, additional prize, auxiliary prize...

subtitle, subheading

side effect (of a vaccine), side reaction

by-product, spin-off, outgrowth...

side job, sideline, subsidiary business

second in command (of an army), vice-captain, fourth athlete to compete in a 5-on-5 team competition (kendo...

countersignature

grave goods, burial accessories

adjutant, aide, aide-de-camp

side dish, supplementary food

helper (e.g. for a sick person), assistant, bridesmaid...

supplementary reader

secondary

additional income

secondary cause

vice-envoy, deputy delegate

vernier

assistant, associate

copy, duplicate

assistant umpire, assistant referee

suprarenal body, adrenal glands

secondary rainbow

duplicate, copy