分类下列单词，说明它们属于哪个词性：


apple, table, run, happy, slowly, quickly, sadness, cleverness
- apple: 名词 (nou)
- table: 名词 (nou)
- run: 动词 (verb)
- happy: 形容词 (adjective)
- slowly: 副词 (adverb)
- quickly: 副词 (adverb)
- sadness: 名词 (nou)
- cleverness: 名词 (nou)