periodicKK [ˏpɪriˋɑdɪk] /ˌpɪɹiˈɑdɪk/形容詞1定期的、週期性的The machine requires periodic maintenance to stay in good condition.這台機器需要定期保養才能維持良好狀態。2間歇性的、不時發生的We still get periodic power outages during the summer months.夏季期間我們還是會間歇性地停電。3週期的化學Every element in the periodic table has an atomic number.週期表上的每個元素都有原子序。