The second pattern, مِفْعَلَةٌ, has:
Word / formMeaning / explanation
مِفْعَلَةٌsingular.
مِفْعَلَتَانِdual.
مَفَاعِلُbroken plural.
For example, مِكْنَسَةٌ is a broom, مِكْنَسَتَانِ means two brooms and مَكَانِسُ is a plural of brooms.
The final tāʾ marbūṭah becomes tāʾ with the dual ending and does not survive as a simple suffix in the broken plural.
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Ism al-Ālah: Definition, Three Patterns, Paradigms and Formation
The second pattern, مِفْعَلَةٌ, has:
Word / formMeaning / explanation
مِفْعَلَةٌsingular.
مِفْعَلَتَانِdual.
مَفَاعِلُbroken plural.
For example, مِكْنَسَةٌ is a broom, مِكْنَسَتَانِ means two brooms and مَكَانِسُ is a plural of brooms.
The final tāʾ marbūṭah becomes tāʾ with the dual ending and does not survive as a simple suffix in the broken plural.