How can I stop my dog (adult) from biting?

Similarly to puppies, older dogs can bite out of boredom, being overtired, overstimulated, among other reasons.

You can redirect a bite with a toy, or a strong scent (like chicken, bacon, ham) however if you're worried your dog's behaviour having changed negatively, please consult with a reputable, positive reinforcement trainer so they can properly address the root of the issue, while helping you prevent future bites.