經劫之間人壽一增一減也。俱舍論光記十二曰：「增減者，從人壽十歲，增至八萬歲，復從八萬歲，減至十歲。」此一增一減之間，新譯家稱曰中劫。俱舍論十二曰：「此洲人壽經無量時，至住劫初，壽方漸減。從無量減，至極十年，即名為初一住中劫。此後十八，皆有增減。謂從十年增至八萬，復從八萬減至十年，爾乃名為第二中劫。次後十七，例皆如是。於十八後，從十歲增，極至八萬歲，名第二中劫。」舊譯家名此一增一減曰小劫。佛祖統紀三十曰：「如是一減一增，為一小劫，二十增減為一中劫。」
A kalpaduring which a human lifetime increases from ten years to 80,000 years and then decreases back to ten. At the end of the first century the increase is to 11 years; at the end of the second century to 12 years, and so on till a lifetime lasts 80,000 years; then decrease follows in the same ratio till 10 is reached. The whole period of accretion and declension covers a smallkalpa, i.e. 16,800,000 years; also called 中劫.
一一增一減 指人壽於劫波之間一增一減。推算劫波，人壽從八萬四千歲，每百年減壽一歲，如此至十歲，是為一減；復由十歲，每百年增壽一歲，至八萬四千歲，是為一增。如此一增一減，鳩摩羅什等舊譯家稱為一小劫，法意譯之提婆達多品及新譯家皆稱為一中劫，其梵語均為 antara-kalpa。〔立世阿毘曇論卷九、大毘婆沙論卷一三五、俱舍論卷十二、佛祖統紀卷三十〕（參閱「劫」3541）p128