Is danger an antonym for harm?

Danger and harm are not antonyms. They are both related to the idea of causing damage or injury, but they have different meanings.

Danger refers to the possibility or likelihood of harm occurring. It is a potential threat. For example, if you are walking near a cliff, you are in danger of falling.

Harm refers to actual damage or injury that has occurred. It is a negative consequence. For example, if you fall off a cliff, you will be harmed.

So, danger is not the opposite of harm. Danger is the potential for harm, while harm is the actual occurrence of damage or injury.