What terms does Esther use to describe herself? How does she compare or contrast herself with Doreen and others in New York City, or with Joan and other patients in the hospital?

Esther Greenwood, the protagonist of Sylvia Plath’s The Bell Jar, takes center stage in this novel of self-discovery and alienation. The reader’s introduction to Esther instantly creates a strong juxtaposition between the two worlds she inhabits: though she is a young woman with an enviable lifestyle working at a trendy magazine and with a social life to match, internally she feels like an inanimate object, a "numb trolleybus."
How Esther describes herself encapsulates the main theme of the novel, which is Esther’s identity, or lack of identity for that matter. Like any young person, The Bell Jar’s protagonist is looking for role models all around her, the most eccentric of them being the confident and boy-chasing Doreen, which only leaves Esther feeling more lacking of an identity in comparison. After spending a night with Doreen and all her wild antics, Esther takes a long walk home, unable to recognize herself in the shop-front mirrors: she is just "wrinkled and used up," or "the reflection in a ball of dentist's mercury." There are no other women in the novel helping to boost Esther’s self-worth: the editor of the magazine she works for thinks Esther has no motivation or direction, which the young woman soon internalizes, thinking,

A girl lives in some out-of-the way town for nineteen years, so poor she can't afford a magazine, and then she gets a scholarship to college and wins a prize here and a prize there and ends up steering New York like her own private car. Only I wasn't steering anything, not even myself.

The second part of the novel replaces a tale of growing up with one of mental deterioration and suicidal ideation. Here Esther can only model herself on other patients in the hospital—some with no identity to speak of, like the lobotomized Valerie—and leaving the asylum is treated by Esther as "a ritual for being born twice." How Esther describes herself by the end of the novel is simply alive, her heart reminding her with each beat, "I am, I am, I am."