Emotion: what is it?
Dictionary: Any agitation of mind; feeling
Writing: Characters feeling. Reactions toward the situation.
Where a writer trips up on expressing emotion: They tell it instead of show it.
Show me fears: Shakes, racing heart, panic, sweat, chewing of lips, biting nails.
Show me sadness: twisted stomach, hard sobs, tears, aching eye sockets, loss of appetite.
These are some of the examples. Make your story strong by expressing the emotion. So what kind of examples can you give that shows emotion?