أَمَّا الْعُجْمَةُ، فَشَرْطُهَا أَنْ تَكُونَ عَلَمًا فِي الْعُجْمَةِ
Translation: As for foreign origin, its condition is that the word be a proper name in the foreign language.
أَمَّا: a particle introducing a topic with a conditional force; الْعُجْمَةُ: nominative topic.
فَشَرْطُهَا: fāʾ answering ammā; شَرْطُ: nominative subject of the explanatory clause, هَا: attached genitive pronoun.
أَنْ تَكُونَ: an subordinates the imperfect kāna; عَلَمًا: accusative predicate of kāna, whose subject is understood.
The construction makes the proper-name condition explicit.