Present tense third person: makes amends for or atones for wrongdoing.
From Latin expiare with third-person singular present ending -s. The verb form has been in English since the 16th century, borrowed directly from Latin legal and religious contexts.
The verb 'expiate' is much rarer than you'd expect in modern English, but it appears frequently in legal documents and religious texts because it carries an official, formal weight that 'atone' doesn't quite match.
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