بِمَ :- أداة استفهام مركَّبة من حرف الجرّ الباء ، و ( ما ) الاستفهاميَّة وقد حذفت ألفها لدخول حرف الجرّ عليها ( انظر : م ا – ما ) :- بِمَ تكتب ؟ – { فَبِمَ تُبَشِّرُونَ } . المعجم: اللغة العربية المعاصر
يجب حذف ألف ما الاستفهامية إذا جرت وإبقاء الفتحة دليلا عليها، نحو فيم وإلام وعلام وبم معني اللبيب لإبن هشام ص :١/ ٢٩٩,٣٠٠
Compound word consisting of the preposition “bi” (meaning with) and the particle “ma” (what). It can either be followed by a noun with the meaning of the one that, suitable as a link, or a noun in the genitive case. Examples include “participated with what is useful” and “took the box with what is in it”. Another compound word, “bima,” is an interrogative tool made up of the preposition “bi” and the interrogative particle “ma,” with the alif omitted when followed by a preposition. For example, “with what do you write?” It is important to omit the alif in “ma” in interrogative contexts but retain the vowel as evidence.