grad，gree，gress 级；步；走
1. upgrade
(noun) 升级。(transitive verb) 使升级；提拔；改善
[记] up-（向上）+ grad（级）+ e --> 逐级向上 --> 升级
[用] no need for an upgrade 无须提升
[用] upgrade a system 升级系统
[派] upgradation (noun) 升级，改善
[近] promote (transitive verb) 提升
2. graduate
(noun) 毕业生；学士学位获得者。(transitive verb) 毕业
[记] grad（级）+ u + -ate（名词后缀）--> 完成某一阶段最高级学业的人 --> 毕业生
[用] a high school graduate 高中毕业生
[用] a graduate in history 历史学学士
[派] graduation (noun) 毕业
[派] graduated (adjective) 分等级的
