This is the 4639th most frequent Portuguese word.
dentista
Dentist.
Here, 'dentista' is used as a common noun referring to a professional who specializes in dental care.
Eu tenho uma consulta marcada com o dentista amanhã.
I have an appointment with the dentist tomorrow.
In this case, 'dentista' is a feminine noun agreeing with 'a', the feminine singular definite article.
A dentista recomendou que eu usasse fio dental diariamente.
The dentist recommended that I use dental floss daily.
In this instance, 'dentista' is a masculine noun agreeing with 'o', the masculine singular definite article.