dissertation vs essay

dissertation

noun
  • A formal exposition of a subject, especially a research paper that students write in order to complete the requirements for a doctoral degree in the US and a non-doctoral degree in the UK; a thesis. 

  • A lengthy lecture on a subject; a treatise; a discourse; a sermon. 

essay

noun
  • A written composition of moderate length, exploring a particular issue or subject. 

  • A proposed design for a postage stamp or a banknote. 

verb
  • To move forth, as into battle. 

How often have the words dissertation and essay occurred in a corpus of books? (source: Google Ngram Viewer )