Definition - The accidental omission of a repeated letter (or letters) when making a written copy of a text.
Note: It is the opposite of dittography, the accidental repetition of letters or words when making a written copy of a text.

Example -
Writing omision instead of omission
Note: To omit a final period in a sentence that ends with an abbreviation is an example of conventional haplography (i.e. haplography that isn't considered an error).

Etymology -
The term derives from the Greek haplos, simple or single + graphos, writing.

Oxford English Dictionary -
Its first citation is from 1888:
"Haplography or Lipography … is a special and very common case of omission."
(J. Gow Comp. Classics 55)

Please comment