Incapable of causing harm or danger; safe.
"The small white snake was harmless and simply curled up to sleep in the sun."
In plain English: Harmless means something that cannot hurt anyone or cause any damage.
"The small spider in my bedroom is completely harmless and just wants to spin its web."
Usage: Use harmless to describe something that poses no threat, such as an animal with sharp teeth but gentle behavior. This adjective is often confused with the noun safety when describing a situation rather than an object's inherent nature.
Harmless comes from Middle English and Old English, combining the word for injury with a suffix meaning "without." The term has traveled into modern English with its original sense of being free from danger or damage.