عطف البيان and البدل
In regards to thread: http://www.lqtoronto.com/forums/show...=4751#post4751
al-Badal & "Atf al-Bayaan
البَدَلُ وعَطْفُ البَيَانِ
Atf al-bayaan is not something which students of Arabic need to know in the early stages of their learning the language.
Grammarians say that any instance of atf al-bayan can also be badal al-kulli also except in the following cases:
in atf al-bayaan both the elements should be either be ma"rifah or nakirah. If they differ in this regard, the second element is badal, not atf al-bayaan,
أَسَافَرَ أخُوكَ بلالٌ؟
Here بلال can be both badal as well as atf al-bayaan.
أَعْرِفُ لُغَتَيْنِ العربيةَ والفرنسيةَ.
the second element cannot be atf al-bayaan as the first element is nakirah and second is ma"rifah.
In some cases, atf al-bayaan is an integral part of the sentence, and cannot be omitted, e.g.:
بلالٌ سافرَ الحسين أخوه.
Here, if أخُوه is omitted, the sentence has no meaning.
I think this much is enough to understand the difference between them.