ابجد is one part of the old alphabetic order that was invented by the semitic people which is not used nowadays the order was ابجد هوز حطي كلمن صعفص قرشت ثخذ ضظع whenever u find Abjad alone it mostly refer to that old order but no specific meaning to it its like saying (ABC) and for Abjadeeah its always referred to the alphabetic letters and Abjady always means arranged alphabetically in alphabetic order

"أبجد" is made up of the first four letters in the old order of the Arabic alphabet. As far as I know, it does not carry any meaning in itself. "أبجدية" means "alphabet". We do not say: "أبجد اللغة العربية", but rather "أبجدية اللغة العربية".