Learn Farsi: گوهرشناسان این گوهر را کم‌نظیر می‌دانند. - The gemologists consider this gem unparalleled.

This sentence uses a predicative complement, which is a common structure for verbs of consideration like dânestan (to know or consider). You simply place the definite direct object and râ (in gohar râ) right before a bare adjective (kam-nazir). The 'to be' is naturally implied by this structure, shifting the verb's meaning from simply 'knowing' to 'considering [something] [as something].'

Can we change the word order and put the adjective kam-nazir before the object marker râ?

No, because kam-nazir is not an attributive adjective modifying the noun directly (this sentence does not mean 'this unparalleled gem'). Instead, it is the complement describing how the subject views the object. The object marker râ must attach directly to the definite direct object (in gohar), and the complement (kam-nazir) must follow it, placed right before the verb.

How is the subject gohar-shenâs-ân constructed?

It is a compound noun made of gohar (gem or jewel) and shenâs, which is the present stem of shenâkhtan (to know or recognize). This 'noun + present stem' pattern is very common for creating professions and traits in Farsi. The -ân at the end is the formal plural suffix used for animate nouns (people).

What are the root words inside the adjective kam-nazir?