In the sentence "The detective spotted a suspect package on the platform.", the adjective is "suspect."
### Explanation:
- The word "suspect" in this context is an adjective because it describes the noun "package". It means that the package is suspicious or believed to possibly be dangerous or connected to a crime.
The word "suspect" can also be a noun (referring to a person), but here, it is used to describe the "package" and thus functions as an adjective.
So, "suspect" is the adjective in the sentence.
