"Consistency between the law and the subject-matter" is a topic dealing with the relationship between the law and the subject matter (mawḍūʿ). The topic suggests that the subject matter should be consistent with the law or the law should be consistent with the subject matter. For example, according to some traditions, the night prayers may be offered in summer in the early portion of the night because the nights are short. Now the question is whether this ruling is restricted to the fear of missing the night prayer or it is unrestricted from this angle. The late Muhaqiq Khoei (may Allah be pleased with him) says: Although the explicit texts (nuṣūṣ) requires that they be not restricted but the relationship between the law and the subject-matter requires that it be restricted because what is commonly understood is that it is permissible to offer the night prayers in the early portion of the night. It is due to the shortness of the night that one often remains asleep at the end of the night. Therefore, it is not possible to use the permission of offering the prayers in the early portion of the night in an absolute manner, even if there is no fear of falling asleep at all. (Khoei, Encyclopedia of Imam Al-Khoei, vol. 11, p. 280)
The context of "consistency of law and subject-matter" is one of the most fundamental and comprehensive contexts relating to understanding the word, and among the heading of this context and its functions are one of the important topics that show the importance and benefit of this context.  But what has been done about the functions of this context in the existing books and writings is that sometimes a few cases of the functions and roles of this context have been mentioned, and sometimes only cases of applications have been mentioned under the title of functions. However, considerable investigation in the various and numerous roles of this context, categorizing them and dealing with their role, and mentioning their applications and examples for each title, is something that has not been undertaken in any writing. However, there are multiple functions for the consistency of the law and the subject-matter, in the understanding of the evidence that this article is about these matters, according to which one can investigate the jurisprudence which this writing undertakes to explain.