Sentence:  At these times he felt a kind of pain in his upper chest , but it was an objective pain , in no way different from others in intensity and <WSD>not</WSD> different in kind ; it was like the bandaged wound on the back of his head which occasionally throbbed ; it was merely another part of his weakness . 
Meaning of the word marked with <WSD> tags:  negation of a word or group of words