n.

1. 【哲】單子
2. 【生】單細胞生物
3. 【化】一價物
4. 【物】單軸

n.

1. technical a single unit; the number one.
2. Philosophy  (in the philosophy of Leibniz) an indivisible and hence ultimately simple entity, e.g. an atom or a person.
3. Biology,  dated a single-celled organism or a single cell.