What does "I beg to differ" mean?

A polite, formal way of saying "I disagree." It expresses disagreement while maintaining respect for the other person.

"You say it's not possible, but I beg to differ."
"With respect, I beg to differ on this point."

Formal and slightly old-fashioned. It's courteous - "begging" implies you're asking permission to hold a different view. In modern speech it can sound slightly theatrical or ironic.

In formal debates, professional discussions, or written disagreements where you need to be polite but firm. In casual conversation, it often signals that someone is being deliberately formal for comic effect or emphasis.

• "I disagree" - direct and clear
• "Actually, I think..." - softer introduction to a counterpoint
• "With respect, that's not quite right" - professional pushback
• "I'm not sure that's accurate" - gentle disagreement

Formal to ironic. Genuine use in professional writing; often used with a knowing tone in speech.