This is the 11953rd most frequent Portuguese word.
quimioterapia
Chemotherapy: a treatment using chemical substances, especially to treat cancer.
In this sentence, 'quimioterapia' is used as a subject noun referring to a medical treatment for cancer.
A quimioterapia é um dos tratamentos utilizados contra o câncer.
Chemotherapy is one of the treatments used against cancer.
Here, 'quimioterapia' is used as a direct object noun indicating the treatment the person started.
Ela começou a quimioterapia na semana passada para tratar a doença.
She started chemotherapy last week to treat the illness.
In this context, 'quimioterapia' is used as part of a time expression referring to the ongoing state of undergoing the treatment.