Denotation is the dictionary definition. It is a non-emotional, literal definition of the word. Connotation, on the other hand, is the emotional meaning of the word. For example, many people consider “skinny” to have a negative connotation and “thin” to have a positive one, even though they have similar denotations.
“Dull” has a negative connotation. Rather than the opposite of bright, emotionally it brings up negative ideas. “Inspire,” on the other hand, has a positive connotation. We like people who inspire others! Life, on the other hand, does not really have strong emotional connotations of different emotional meanings.