Did Allah and His Chosen One (peace be upon him) prohibit the juristic application of the term "bid'ah" (innovation) while permitting its linguistic application, or has bid'ah been forbidden in all its applications?

The Prophet warned against innovation (bid'ah) in religion, as in the hadith: "Whoever innovates into this affair of ours that which is not from it, it is rejected." As for innovations in customs, such as a flour sifter or academic titles, they are not blameworthy innovations according to Islamic law, because they fall under matters that have been left unspecified and remain permissible in their original state. And applying the word "Shaykh" to a young scholar has no legal prohibition; rather, it is linguistically permissible for veneration, even though it is more commonly used in the language for someone whose age is evident.