One of the differences between a memoir and a reflective essay is the time period written about. Memoir comes from the French word "memoire," literally meaning memory. Memoirs are written about a person's memories and experiences. A reflective essay can be written about whatever the writer wishes to discuss, including future plans or current happenings.
Both reflective essays and memoirs are written from the first person point of view; however, their topics can be quite different. Reflective essays can be written about anything that moves the writer. The topic does not need to be deep or significant. A reflective essay can be a simple reflection on what the writer sees as he takes a morning walk. A memoir is written about one or more events in a person's life that has held great significance, or made a large impact on him and/or history. Many memoirs are written by people who have lived through an important time period.
A reflective essay is a means for the writer to share thoughts, ideas, personal beliefs and convictions. Many reflective essays are written to persuade the reader by using a personal anecdote or experience. A memoir is written to share an event from the writer's life that has shaped or changed him. In a memoir, the writer usually discusses the implications of the event or events, and seeks deeper meaning through his writing.
Although there are no strict rules about the length of a memoir or a reflective essay, the two usually differ in length. By definition, an essay is a short, nonfiction account written in prose. A long piece of prose would not be considered an essay. A memoir, although typically shorter in length than an autobiography or biography, can be much longer than an essay and still be considered a memoir.