The author s feeling about a subject or topic, which is evidenced in word choice, is called tone.
Explanation;
Tone indicates or describes the attitude of the author towards a given subject or topic. The author's attitude is expressed through the choice of words he or she uses.
The tone is described by adjectives such as ironic, cynical, intense, sarcastic etc. It may be expressed by use of syntax, point of view, diction, etc.
The tone may change very quickly or may remain the same throughout a topic or a story.