"What is the difference between 두려워 마 and 두려워하지 마 (Does 두렵지 마 exist??)" The adjective 두렵다 is one of those special adjectives for expressing a first person emotion. They are words of direct emotions, like 좋다, 싫다, 기쁘다, 슬프다, 두렵다, 힘들다, 아쉽다, etc. In the present tense, these adjectives can only be used for the first person. For the second and third person, we use the verbs 좋아하다, 싫어하다, 기뻐하다, 슬퍼하다, 힘들어하다, 아쉬워하다, etc. Also note that Korean has verb negators 않다 ("not" in general), 말다(will not), and 못하다(cannot). 말다 means intentionally choosing not to do something, while 않다 means a simple, broader negation. As you suggested, the emotion adjectives are about natural state or reaction, so 말다 can't be used for them. Only 않다 works for them. For example: - 나는 개가 무서워 => 나는 개가 무섭지 않아. (무섭지 말다 doesn't exist) - 나는 행복해 => 나는 행복하지 않아. When their verb forms are used for the second or third person, both 않다 and 말다 can work. But 말다 is for imperative phrases asking the person to be certain way, not about how they naturally are. - 그는 개를 두려워하지 않아. (He does not fear dogs = He's not afraid of dogs). - 개를 두려워하지 마. Don't be afraid of dogs. (imperative - asking the person not to be afraid) 두려워 마 is just a contraction of 두려워하지 마, as 걱정 마 is of 걱정하지 마. When 하다 functions as a helper verb with another verb or noun as in here, it can sometimes be abbreviated out. - 걱정하지 마 == 걱정 마(imperative); - 슬퍼하지 마 == 슬퍼 마. - 무서워하지 마 == 무서워 마. But this abbreviation is not universal. Some less often used phrases might sound odd if abbreviated this way.