P.S.的全称是“postscript”
“postscript”这个词表示“信末签名后的附笔,又及”,通常的搭配是“postscript to sth”,比如说:
She mentioned in a postscript to her letter that the parcel had arrived.(她在信末附笔中说包裹已寄到。)
其实这个词是来源于拉丁语“post scriptum”,表示“written after”的意思,也可以说是“that which comes after the writing”的意思。
而postscript的这个缩写,除了可以写成“P.S.”外,还可以写成“PS.”、“PS”或这“p.s.”