Which of the following words has a positive connotation: Odor, Smell, Stench, or Aroma?

The word aroma has positive connotation.

These words have different connotations.

Word smell is neutral,

Words odor and stench are describing unpleasant smell so they are negative.

Aroma is a nice smell, so it has positive connotation.

Note: These words are not proper nouns, so it is not necessary to capitalize them, unless they are at the beginning of a sentence.