Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
benign, benignant, malign, malignant (adj.)
These pairs are antonyms. Benign means “kindly, pleasant, beneficial,” and in medicine specifically “not malignant,” as in a benign tumor. Malign means “evil, injurious, very harmful,” and “malignant,” as in His look was malign and full of hate. Malignant means much the same as malign, “malevolent, highly injurious, evil,” and in medicine specifically it describes an abnormal growth, one likely to grow and therefore likely to kill, as in a malignant tumor. Benignant is built on analogy with malignant and means “kindly, pleasant, beneficial,” and in medicine specifically “not malignant.” Benign and malignant are the higher-frequency adjectives, especially in the medical senses, but all four are Standard.
