post·script 
(pōstskrĭpt′, pōsskrĭpt′)
(pōstskrĭpt′, pōsskrĭpt′)n. Abbr. PS
1. A message appended at the end of a letter after the writer's signature.
2. Additional information appended to the manuscript, as of a book or article.
[Medieval Latin *postscrīptum, from neuter past participle of Latin postscrībere, to write after : post-, post- + scrībere, to write; see skrībh- in the Appendix of Indo-European roots.]