Compare the root and derived pattern:
FeatureForm IForm II
Patternفَعَلَفَعَّلَ
Rootʿ-l-mʿ-l-m
Exampleعَلِمَعَلَّمَ
Broad meaningHe knewHe taught someone
Gemination marks the second radical, not the creation of a new root letter. It may signal an additional semantic feature, but the feature must be established from the example.
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Compare the root and derived pattern:
FeatureForm IForm II
Patternفَعَلَفَعَّلَ
Rootʿ-l-mʿ-l-m
Exampleعَلِمَعَلَّمَ
Broad meaningHe knewHe taught someone
Gemination marks the second radical, not the creation of a new root letter. It may signal an additional semantic feature, but the feature must be established from the example.