This is the 4336th most frequent Spanish word.
same
The word "same" does not exist in Spanish.
Here, 'mismo' is used as an adjective to indicate that the teacher read the identical book being referred to.
El mismo libro fue leído por la profesora.
The same book was read by the teacher.
In this case, 'mismo' serves as an adjective modifying 'tiempo' to express that the arrivals occurred simultaneously.
Ellos llegaron al mismo tiempo.
They arrived at the same time.
Here, 'mismo' functions as a noun to denote an identical or similar object or concept that is desired by both parties.