Use 'remarry' when discussing relationships after a previous marriage has ended legally or by a spouse's death. She wasn't sure if she would ever remarry after the divorce.
Pro Tip 2/3
Not Automatic
'Remarry' implies a deliberate choice; it's not something that happens without a former spouse's consent or action. He took his time to heal before deciding to remarry.
Pro Tip 3/3
Legal Implication
The term 'remarry' signifies that someone has legally formalized a new marriage, not just moved in with someone. After the paperwork was finalized, they chose to remarry in a quiet ceremony.