A more thorough explanation:

Drug dependence is when a person feels like they need a drug to function normally. This can be because of a psychological need or a physical need.

For example, someone who is addicted to opioids may feel like they cannot function without taking the drug. They may experience withdrawal symptoms like nausea, vomiting, and muscle pain if they try to stop taking the drug.

Another example is someone who is addicted to nicotine. They may feel like they need to smoke a cigarette to feel calm or focused. They may also experience withdrawal symptoms like irritability and anxiety if they try to quit smoking.

These examples illustrate how drug dependence can affect a person's life and make it difficult for them to quit using the drug.