To form مِفْعَلٌ according to the source rule:
1. Remove the active imperfect prefix.
2. Replace it with مِ, mīm bearing kasrah.
3. Give the second root letter fatḥah, retaining it if already present.
4. Supply the appropriate nominal tanwīn.
يَضْرِبُ ← مِضْرَبٌ
The kasrah on rāʾ changes to fatḥah. The imperfect prefix يَ becomes مِ, creating the instrument-noun pattern rather than another finite verb.
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First derivation rule: mifʿal
Ism al-Ālah: Definition, Three Patterns, Paradigms and Formation
To form مِفْعَلٌ according to the source rule:
1. Remove the active imperfect prefix.
2. Replace it with مِ, mīm bearing kasrah.
3. Give the second root letter fatḥah, retaining it if already present.
4. Supply the appropriate nominal tanwīn.
يَضْرِبُ ← مِضْرَبٌ
The kasrah on rāʾ changes to fatḥah. The imperfect prefix يَ becomes مِ, creating the instrument-noun pattern rather than another finite verb.