PS       
noun [ C ] uk/ˌpiːˈes/ us/ˌpiːˈes/
 (信末)附言,又及
used when you want to add extra information at the end of a letter or email
  Love from Sophie. PS Say hi to Gemma. 爱你的索菲。又及:向杰玛问好。 
 She added a PS asking for your address. 她加了一条附言问你的地址。 
 - More examples
 - PS, don't forget to bring your raincoat!
 - PS, Max send his love to you.