Proofreading: Proofreading is the stage of the editorial process that takes place after a work has already been copy edited and typeset. It entails a review of your work for typos and for correct capitalization, grammar, punctuation, and spelling; a cross-check of chapter headings and page numbers in the table of contents with headings and page numbers in the text; a cross-check of page headers across the book; and an evaluation of the quality and alignment of tables, figures, and graphs.
However, if your work has not already been copy edited or typeset, your piece may still fall under this level of editing if you feel your writing is quite polished and simply needs a review for typos and correct capitalization, grammar, punctuation, and spelling.
With this level of editing, please note that no suggestions will be made to adjust awkwardly worded sentences, to reorder text for better reading, to correct discrepancies between passages of information, to make the changes necessary to ensure your work adheres to a particular style (e.g., APA style, Chicago style, a particular house style designated by you, etc.), and so forth. In other words, proofreading entails a simple read of your text to ensure that there are no glaring errors.
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Copy Editing: In addition to a review of your work for typos and for correct capitalization, grammar, punctuation, and spelling, copy editing entails an edit of your work for general clarity of expression; consistency of facts, statements, and spellings of particular words (e.g., British English spelling vs. American English spelling) or proper nouns within your work; and conciseness of your material (i.e., an elimination of unnecessary repetition). Copy editing also involves (a) ensuring that your work adheres to a particular style (e.g., APA style, Chicago style, a particular house style designated by you, etc.), (b) cross-checking table or figure captions and cross-checking in-text citations or endnotes with references, and (c) flagging items in your work that may appear to be copyrighted and would therefore require permission before publication can occur.
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Substantive Editing: Substantive editing entails the extent of editing carried out at the copy editing level in addition to one or more of the following: (a) a significant reworking of your text, which would include a major overhaul of the wording of individual sentences; (b) a reorganization of sentences, paragraphs, or chapters for better clarity and flow; and (c) suggestions for the inclusion of additional information to enhance the clarity and effectiveness of your work.