odor
[C/U] Both
pl: odors
This term carries a strong negative bias in modern usage. While technically a neutral word for any scent, it is almost exclusively deployed to describe smells that are offensive, stale, or biologically repulsive, such as body odor or rotting garbage. In contrast, words like fragrance or aroma are reserved for pleasant smells. Using odor to describe a flower would sound clinical or oddly suspicious, as the word evokes a sense of chemical sharpness or organic decay.
Countable when referring to a specific, identifiable scent like a gas leak. Uncountable when discussing the general quality of smelling, such as a room having a strong odor.