Textual variants in manuscripts arise when a copyist makes deliberate or inadvertent alterations to a text that is being reproduced.
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).
They may resort to performing a rearranging of words to retain the overall meaning without compromising the context.
"[2] 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.