trans- "across, beyond" + gradi (past participle gressus) "to walk, go"

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an act that goes against a law, rule, or code of conduct; an offense:

｟かたく｠ 違反, 犯罪; (宗教･道徳上の)罪(sin)

e.g. I'll be keeping an eye out for further transgressions

e.g. her transgression of etiquette.