The original case, new case, ruling, and cause

Analogy: Original and New Cases, Common Cause, Co-variation and Elimination

The four principal elements of analogy are:
Original case (aṣl): the particular whose judgment is already known.
New case (farʿ): the particular for which the judgment is sought.
Judgment (ḥukm): what is established for the original and proposed for the new case.
Cause or unifying feature (ʿillah / jāmiʿ): the relevant shared meaning proposed to justify the transfer.

If the unifying feature is not relevant to the judgment, cataloging similarities between the cases cannot complete the inference.