1.. senior senile junior
senior: 指年长的，最高年级的， 资深的，级别地位高的
senile ::if old people becom senile.they become confused.can no longer remember things.and are unable to look after themselves. senile demential 老年痴呆
junior: a junior official or employee holds a low-ranking position in an organization or profession
she is my junior by three years 她比我小三岁
Tom is my junior Tom 是我的晚辈
美国中学或大学的三年级学生
Mary, a junior, will graduate next year.