A conditional statement begins with the word "when"

That is not accurate. A conditional statement typically begins with the words "if" or "when." For example:

- "If it rains, I will bring an umbrella."
- "When the temperature drops, I will wear a jacket."

The word "when" is used to indicate that a certain condition will definitely occur at some point, while "if" is used to express a possibility or uncertainty about the condition.