filename extension
 文件擴展名


 filename extension
 檔案延伸名稱


 filename extension
      n : a string of characters beginning with a period and followed
          by one to three letters; the optional second part of a PC
          computer filename; "most applications provide extensions
          for the files they create"; "most BASIC files use the
          filename extension .BAS" [syn: extension, {file name
          extension]