A sound word (ṣaḥīḥ) is one whose radicals contain no hamzah, no weak letter, and no pair of identical radicals of the kind relevant to doubling. All three conditions matter.
ضَرَبَ has three distinct strong radicals: ض، ر، ب.
بَعْثَرَ shows that a quadriliteral root can also be sound.
The same basic classification can apply to nouns, as illustrated by رَجُلٌ and جَعْفَرٌ. A sound word is not defined by being a verb or by having a specific meaning.
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The Sound Category
The Seven Morphological Classes: Sound, Hamzated, Weak and Doubled
A sound word (ṣaḥīḥ) is one whose radicals contain no hamzah, no weak letter, and no pair of identical radicals of the kind relevant to doubling. All three conditions matter.
ضَرَبَ has three distinct strong radicals: ض، ر، ب.
بَعْثَرَ shows that a quadriliteral root can also be sound.
The same basic classification can apply to nouns, as illustrated by رَجُلٌ and جَعْفَرٌ. A sound word is not defined by being a verb or by having a specific meaning.