Antonym

/ˈæn.tə.nɪm/

noun — “the polite way words argue with each other — ‘yes’ versus ‘no’ at the dictionary debate club.”

Initialism

/ɪˈnɪʃ.əl.ɪ.zəm/

noun — “the cousin of acronyms that refuses to be spoken as a word — it insists on spelling itself out, letter by letter.”