Can someone explain the sentence 频率是在宇宙中最重要的概念之一 in english?
I read it as Frequency is the most important concept in the universe
Literally - Frequency is the single most important concept in the universe.

Question

Answer

之一 = one of

频率  是  在  宇宙  中  最重要的  概念  之一

frequency is one the most important concepts in the universe

Answer

one of = 之一
concept (NOUN)= 概念

In english, "one of" is followed by the NOUN; in chinese, the NOUN is followed by "one of".

Answer

我感觉这句中文这样更好：
在宇宙中，频率是最重要的概念之一。
有个‘之一’， 就加一个‘one of',  one of the most important....