The two signal words used on WHMIS 2015 labels are "Danger" and "Warning".

• "Danger" is used for more severe hazards, indicating a higher level of risk with products that might be extremely flammable, corrosive, or highly toxic.
• "Warning" is used for less severe hazards, indicating moderate risk and requiring careful handling.

These signal words quickly communicate the level of hazard to ensure safe handling of hazardous products.