Physical dependence means that your body becomes used to a certain medicine or substance and now needs it to feel normal. Kind of like how you need food to feel full or sleep to feel rested.
When you take a medicine or substance for a long time, your body gets used to it and changes so it needs more of it to keep working as it should. If you suddenly stop taking the medicine or substance, your body might not work right because it has become dependent on it. This can cause things like feeling sick or having withdrawal symptoms.
It's important to remember that physical dependence is different from addiction, which is when someone feels like they can't stop using a substance even if it's causing harm. With physical dependence, someone can be using it responsibly and still become dependent.
In summary, physical dependence means that your body needs a medicine or substance to function normally and can have negative effects if you suddenly stop using it.