Comment by jltsiren

Academic terminology tends to be inconsistent, vary from person to person, and evolve from year to year. The usual expectation is that you should define the terms you use if their exact meaning is important. Otherwise people will misinterpret them.

"Abjad" seems to be a more specific term than "alphabet". Sometimes it is used as a subcategory of "alphabet" (as in "abjad alphabet") and sometimes the terms are mutually exclusive.