This is the 8161st most frequent Portuguese word.
substituta
"Substituta" means "substitute" or "replacement" (feminine form).
In this sentence, 'substituta' is used as a noun to describe someone acting in place of another temporally, in this case, a teacher.
A professora substituta assumiu a turma durante a ausência da titular.
The substitute teacher took over the class during the absence of the main teacher.
Here, 'substituta' is deployed as an adjective modifying 'atriz', indicating readiness to take over the role when necessary.
Ela é uma atriz substituta, pronta para atuar se a principal não puder.
She is a substitute actress, ready to perform if the main one cannot.
Here, 'substituta' describes the object intended to serve as a replacement for the original car engine part.