싫다 is an emotive word that expresses the feeling directly, whereas 싫어하다 is indirect and more general. 싫다, 좋다, 기쁘다, 슬프다, and other such words are special in that they can only be used for the first person "I". In addition, instead of the usual S+O+V structure, they are used in S+V form, where S is the object of the emotion. For example, (나는) 네가 싫다 instead of 너를 싫다 (note 가 in the first sentence). For the second and third person, you must use 싫어하다 in S+O+V structure, as in 그는 너를 싫어한다. You can think of it as similar to "I loathe (obj) ..." vs "I am loath to (obj)...", although it's not a perfect parallel. The -하다 version of some words are also used for the first person with a modified meaning. For example, 좋아하다 and 싫어하다 mean general preferences when used for "I" instead of a emotional reaction. In most cases however, the -하다 versions are for the second and third person only. Examples: - 나는 고양이가 좋다. - 어머니는 고양이를 싫어하신다. - 나는 그 소식을 듣고 기뻤다. - 그녀는 그 소식을 듣고 기뻐했다. - 난 그것이 안타까웠다. - 그는 그것을 안타까워했다.