Learn Farsi: تفکر عمیق یکی از بهترین ویژگی‌های انسان است. - Deep thought is one of the best human traits.

The word tafakkor exactly follows the tafa'ol pattern (ta-C1-a-C2-C2-o-C3). Its three-letter root is f-k-r, which you already know from the word fekr (thought). This Form V pattern often denotes a deliberate, gradual, or intensive action, which is why tafakkor translates to deliberate contemplation or deep thought rather than just a passing idea.

Does tafakkor mean the exact same thing as fekr?

While they share the same root, they are not completely interchangeable. fekr is the everyday word for a thought, idea, or the general act of thinking. Because tafakkor uses the Form V structure, it carries a heavier, more academic sense of pondering or deliberate reasoning.

Why doesn't the superlative adjective behtarin have an Ezafe linking it to vizhegi-ha?

In Farsi, superlative adjectives (those ending in -tarin) are placed before the noun they modify, and crucially, they do not take an Ezafe. You just say behtarin vizhegi-ha. The only Ezafe in this noun phrase is the -ye at the end of vizhegi-ha-ye, which links the whole phrase to ensan (human).

Why is vizhegi (trait) in the plural form here? I thought superlative adjectives usually take singular nouns.

You are correct that a superlative usually takes a singular noun in Farsi (for example, behtarin vizhegi means the best trait). However, because this sentence uses the construction yeki az (one of), the noun must be pluralized, exactly like how we say one of the best traits in English.