• 'Mea culpa,' at times
• 'My bad,' for one
• An expression of regret
• Excuse, sometimes
• Expression of regret
• Fight stopper
• Guilty plea?
• I'm sorry or My bad
• It may be owed
• Palliative pronouncement
• Quarrel stopper, maybe
• Retraction
• Something often owed
• Something owed, maybe
• A poor example
• An expression of regret at having caused trouble for someone
• A formal written defense of something you believe in strongly