The document discusses antonyms, which are words that have opposite meanings. It provides examples of word pairs that are antonyms, such as speedily/plodding, ferocious/tame, hard/soft, immense/small, generous/miserly, affluent/impoverished, feeble/strong, noisy/relaxing, towering/short, permanent/unstable, plentiful/sparse, positive/negative, powerful/weak, praise/criticism, private/public, problem/solution, profit/loss, quality/inferiority, random/specific. The document also lists some common antonym word pairs and provides references for additional information.