Here's how:
Synonyms:
* Cunning: A sly fox is a cunning fox.
* Devious: A sly plan is a devious plan.
* Shrewd: A sly businessman is a shrewd businessman.
* Wily: A sly salesman is a wily salesman.
Antonyms:
* Honest: A sly person is the opposite of an honest person.
* Open: A sly remark is the opposite of an open remark.
* Straightforward: A sly approach is the opposite of a straightforward approach.
* Naive: A sly person is the opposite of a naive person.
It's important to understand the context and the word being compared to determine whether "sly" is a synonym or antonym.