TL;DR: The three terms get used interchangeably in casual conversation, but they describe different kinds of books with different structural requirements my memoir process, different reader expectations, and different markets. I’ve written about a lifelong-dream memoir. The wrong category for your project produces a book that disappoints whoever reads it because they were expecting something else. Here are the actual definitions. What each form requires the author to do. The situations where each makes sense. And how to tell which one you should be writing, before you commit to the project.
The three forms, defined plainly
A memoir is a book by the author about a specific theme, period, or thread of the author’s life, told in scene and reflection, with literary technique. A memoir doesn’t try to cover the whole life. It picks a narrow piece of it and goes deep. For more, see co-author versus hire a ghostwriter and Writing about family in a memoir without a lawsuit or a family rupture.
The reader’s experience is being inside the author’s specific perspective on the chosen material. A memoir of a difficult marriage. A memoir of caring for a dying parent. A memoir of building and losing a company. Each selects a piece of the life and works it deeply.
An autobiography is a book by the author about the author’s whole life, told more or less chronologically, with the goal of producing a full record. The reader’s experience is following the trajectory of a life from beginning to current present. Structure is biographical instead of thematic. Readers expect breadth over depth, completeness over selection, the facts and arc of an interesting life from childhood onward.
A biography is a book about a person other than the author, researched and written by the author. The author isn’t the subject. The reader’s experience is learning about someone the author has investigated, with the author as guide and analyst instead of as the focus. Biographies can be authorized, where the subject cooperates with the author, or unauthorized, where the author works from public records and interviews with third parties.
What does memoir require?
Memoir requires three things many authors don’t realize when they start. First, the willingness to narrow the scope to a specific theme or period and leave the rest of your life out of the book. The memoir about your marriage doesn’t also cover your career. The memoir about your career doesn’t also cover your divorce, except where the divorce affected the career arc.
Second, the willingness to go deep on narrow material. That means writing in scenes, including the detail, and putting yourself on the page in specific ways your professional self would normally edit out. Third, the willingness to be honest about the harder material, because memoir without the harder material reads flat.
Many authors who say they want to write a memoir actually want to write an autobiography. The signs are wanting to cover the whole life, wanting to include every notable event, and resisting the narrowing the form requires. That’s a real preference and it’s fine, but it produces an autobiography, not a memoir, and the marketing position for those two books is different. An honest identification of which form you’re actually writing helps the project succeed in its own category instead of failing as the wrong category.
What autobiography actually requires
Autobiography requires the comprehensiveness memoir refuses. The author covers childhood, formative experiences, career, relationships, achievements, setbacks, and the arc of the whole life through to the present. Structurally biographical, the work has chapters that follow time instead of theme. The author has to be willing to include material across many topics instead of going deep on one or two. The work is often longer than memoir, sometimes substantially.
The market for autobiography is real but different from memoir. Autobiographies sell to readers interested in the specific life as a whole. That usually requires fame, a notable career, or an unusual life in some other sense. The reader is committing to spending time with the full arc of someone’s life. The hook is the life itself instead of the literary handling.
Authors who aren’t famous or notable can still write autobiographies, but the audience is usually family, descendants, and a small circle of people interested in the specific person. That’s a legitimate purpose and a defensible reason to write the book. It’s not the same business case as a memoir aimed at general readers.
What biography actually requires
From Author Talks
Diana Rubino writes biographical fiction built entirely from real figures, and found Richard III through a book shelved in the wrong spot at her library thirty years ago. She explained the approach on Author Talks.
Biography by an author about someone else is a research project in a way the other two aren’t. The author has to gather material from public records, interviews, archives, and other sources, and then organize it into a portrait of the subject. Journalistic instead of personal, the work has the author render the subject accurately instead of express the author’s own perspective. The reader expects the author to be reliable, the research to be thorough, and the portrait to be fair.
The form is appropriate when the author has access to a subject worth writing about and the skill to do the research and rendering. Most ghostwriting clients aren’t asking for biographies. They’re asking for memoir or autobiography about themselves, sometimes mistakenly called biography in casual conversation. If the project you have in mind is actually about you, you’re writing memoir or autobiography. If the project is about someone else and you’re the writer doing the work, you’re writing biography.
How do you tell which form you should be writing?
Start with the subject. Are you the subject or is someone else? If you’re the subject, you’re writing memoir or autobiography. If someone else is the subject and you’re the author doing the work, you’re writing biography. That settles the first question.
If you’re the subject, the next question is scope. Do you want to cover the whole life chronologically, or a specific thread or period in depth? If chronological and complete, you’re writing autobiography. If thematic and selective, you’re writing memoir. Authors who want both should consider whether the project is actually two books instead of one, because trying to do both in a single book usually produces a long manuscript that does neither form well.
The third question, mostly for memoir, is which theme to pick. For more on writing a memoir through grief, see Richard’s interview with Catherine Napoli Bruce. Most authors have several memoirs in them, not just one: the professional career memoir, the marriage memoir, the parenting memoir, the grief memoir. The choice of one to write well is the move that produces a book that works. The Book Discovery Intensive handles exactly this question of theme selection, where the working interviews surface which thread of the life carries a full book.
Why misidentifying the form hurts the book
Authors who try to write memoir but produce autobiography end up with books that feel padded, because memoir-thematic discipline is missing and the broad biographical material reads thin without it. Writers attempting autobiography but producing memoir end up with books that feel incomplete, because readers expecting the full life arc keep waiting for the chapter that never comes. Anyone trying to write biography about themselves ends up with books that feel oddly distanced, because the form requires journalistic remove and the material is too personal for the remove to feel right.
The fix is to pick the form deliberately before the project starts and then write to the form. Memoir on a specific theme, with literary technique and depth. Autobiography on the whole life, with comprehensive coverage and chronological structure. Biography on someone else, with research and journalistic care. Each form has its own readership and its own working approach, and the author who commits to a form produces a better book than the author who hedges between forms hoping to capture all three.
Frequently Asked Questions
Related: my memoir process