:salam2:
Why “Logos” is an important in philosophy, psychology, rhetoric, and religion? 
Re: Logos
Peace bro LLK
Logos as you may know is a term in ancient Greek - it means "Word" ... This is not to be confused with "Logo" the English word which is a symbol used for representing intellectual property owned by an individual or organisation.
Logos has various subtle differences in each of the domains it is important for i.e. philosophy, psychology, rhetoric and religion ...
For philosophy - Logos represents an idea in abstraction linked to an a priori and in psychology it represents the initial mode of thought to separate it from other thoughts in rhetoric it is used in a grammatical sense for expressing the marker that gives the purpose behind the words and in religion - specifically Christianity - it refers to the Primal Word - that Instigated Existence. In Islam we have the concept of "Kun" - where we say that Allah (SWT) has just to SAY .... "BE" and it is ...
The summation behind this is that Logos carries a holistic meaning that covers "initialising existence - a word that carries the meaning of and for everything that follows after it"