Textual variants in the Book of Revelation are the subject of the study called textual criticism of the New Testament. Textual variants in manuscripts arise when a copyist makes deliberate or inadvertent alterations to a text that is being reproduced. An abbreviated list of textual variants in this particular book is given in this article below. Most of the variations are not significant and some common alterations include the deletion, rearrangement, repetition, or replacement of one or more words when the copyist's eye returns to a similar word in the wrong location of the original text. If their eye skips to an earlier word, they may create a repetition (error of dittography). If their eye skips to a later word, they may create an omission. They may resort to performing a rearranging of words to retain the overall meaning without compromising the context. In other instances, the copyist may add text from memory from a similar or parallel text in another location. Otherwise, they may also replace some text of the original with an alternative reading. Spellings occasionally change. Synonyms may be substituted. A pronoun may be changed into a proper noun (such as "he said" becoming "Jesus said"). John Mill's 1707 Greek New Testament was estimated to contain some 30,000 variants in its accompanying textual apparatus which was based on "nearly 100 [Greek] manuscripts." Peter J. Gurry puts the number of non-spelling variants among New Testament manuscripts around 500,000, though he acknowledges his estimate is higher than all previous ones. (en)