be senior to 比...年長
be junior to 比...年輕
一般說來,比較級是用than,但以上用法屬特例,而且senior, junior本身就有比較級的意味存在,不能用 more senior or more junior
e.g. She is 5 years senior to me.
She is 5 years my senior.
She is senior to me by 5 years.
1. senior 可當形容詞 (年紀較大的) 或名詞 (較年長者) ，同義詞為 elder，同樣可當形容詞或名詞；您舉的例子 為形容詞， "前者 be senior to後者" 乃前者比後者年紀大的意思，屬有比較語氣之片語，必須記起來。
2. He was senior (or elder) to me by two years. = He was my senior (or elder 屬名詞) by two years. = He was older than me by two years. (older than 屬正式比較級用法)
3. be junior to = be younger than 為前述之相反， "前者 be junior to後者" 乃前者比後者年紀小的意思。
4. He was junior(屬形容詞) to me by two years. = He was my junior(屬名詞) by two years. = He was younger than me by two years. (younger than 屬正式比較級用法)
Good luck to you... from Naughty and Modest Henry...