This is the 378th most frequent Spanish word.
ellas
"They" (feminine).
Subject referring to a group of females.
Ellas fueron al cine juntas.
They went to the cinema together.
Explicitly specifying the subject as a group of females for clarity.
No creo que ellas sepan la respuesta.
I don't believe they know the answer.
The object of the preposition, referring to a group of females.