«القياس في اللغة: التقدير»
Linguistically, qiyas means estimation or measurement.
«قس النعل بالنعل»
Measure one shoe against another.
One object provides a standard for the other. Juristic analogy also relates two cases, but the relevant measure is not physical size; it is the effective basis of a legal ruling. Thus the linguistic illustration introduces the comparison without supplying the complete legal definition.