historian
The word 'historiador' is a noun in Spanish that translates to 'historian' in English. A 'historiador' is a person who studies, researches, and writes about the past, and is regarded as an authority on it. Historians are concerned with the continuous, methodical narrative and research of past events as relating to the human race; as well as the study of all history in time.
The historian is studying the ancient manuscripts.
This is a simple present tense sentence where 'the historian' is the subject who 'is studying' - a present continuous action happening right now - 'the ancient manuscripts' - the object.
My uncle is a famous historian.
This is a simple sentence stating a fact or a general truth, where 'my uncle' is the subject, 'is' is the linking verb showing a state and 'a famous historian' is the complement describing the subject.
As a historian, you have the responsibility to be precise with the data.
This is a complex sentence where 'As a historian' is the dependent clause setting the context, and 'you have the responsibility to be precise with the data' is the independent clause giving the main information.