Idiom idiom

alter ego

C1 Roman origin

Meaning

A second self — either a trusted other person or a different side of yourself.

Examples

SIMPLE

“On stage she becomes her alter ego, a much louder person.”

CONTEXTUAL

“The detective in the novels is widely read as the author's alter ego, down to the address and the bad temper.”

COMPLEX

“For thirty years the chief of staff was the minister's alter ego in the older sense of the phrase — not a projection of him, but a person who could sit in his chair and be obeyed as though he were in it.”

Origin

Cicero built the idea in his essay on friendship. A true friend, he writes, is as it were a second self — alter idem — and the whole point of such a friendship is that you can say anything to the other person because there is no meaningful gap between you.

The Latin tag alter ego, the other I, is a later formulation of the same thought, and for centuries it meant exactly what Cicero meant: your closest confidant, the person who can act for you. Some legal systems still use it that way, for someone empowered to stand in your place.

The modern sense turns it inward. An alter ego is now usually a second version of the same person — a stage name, a pen name, a character an author writes through, or the costumed identity that a comic-book hero puts on when the day job ends.

The Poets' Latinconnected storiesSee all Roman origin →

Horace, Virgil and Cicero, still quoted in the original.

Last updated August 3, 2026