1A particle indicating means or role: 'by' or 'by means of' and also 'as' (in the role of); somewhat literary compared with で／として.
彼は医者にして詩人でもある。
He is a doctor and also a poet (as a doctor, he is also a poet).
連絡は電話にして行ってください。
Please contact me by telephone.
この作品は学者にしては難解すぎるが、一般には読みやすい。
This work is too difficult for a scholar (?), but generally readable.
2Used in causative constructions as in '〜をして', indicating the agent or the person caused to act (literary/older style).
彼をして謝らせたのは私の失言だった。
It was my slip of the tongue that made him apologize.
師をしてその場を収めさせた。
He had the teacher restore order in that situation.
3A connective use after the adverbial form of adjectives or the auxiliary ず, linking and indicating a state or condition (e.g., '安らかにして眠る').
安らかにして眠れ。
Rest peacefully.
静かにして話を聞きなさい。
Be quiet and listen.
4An adverbial/particle use that can add emphasis or indicate a short time interval (e.g., '少しして' = 'a little while later').
少しして彼は戻ってきた。
A little while later he came back.
それにしても彼の才能は素晴らしい。
Even so, his talent is remarkable.
5An archaic conjunction meaning 'and', 'so', or 'then' (literary); seldom used in modern colloquial Japanese.
行きてして還るもの多し（古文表現）。
Many things go and then return (classical expression).
言い終えてして、彼は席を立った。
Having finished speaking, he then stood up.