"Harmful" refers to anything that can cause damage, injury, or negative effects to living beings or the environment. This can include substances like toxic chemicals, behaviors such as smoking, or situations like pollution. The impact of harmful elements can vary, affecting physical health, mental well-being, or ecological balance. In many cases, harmful actions or materials can lead to long-term consequences. For example, excessive plastic waste can harm marine life, while unhealthy diets can lead to chronic diseases. Understanding what is harmful helps individuals and communities make better choices to protect themselves and their surroundings.