To rejoice is to feel great happiness or joy, or to take great pleasure in something.(verb)
When you feel great pleasure after you have had a baby, this is an example of a time where you rejoice.
See rejoice in Webster's New World College Dictionary
Origin: ME rejoissen < inflectional stem of OFr rejoïr < re-, again + joïr, to be glad < VL *gaudire, for L gaudere, to rejoice: see joy
See rejoice in American Heritage Dictionary 4
verb re·joiced, re·joic·ing, re·joic·es verb, intransitive
Origin: Middle English rejoicen
Origin: , from Old French rejoir, rejoiss-
Origin: : re-, re-
Origin: + joir, to be joyful (from Vulgar Latin *gaudīre, from Latin gaudēre; see gāu- in Indo-European roots).
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