Inadvertent (adjective)

1. Not done or made with intention or on purpose; unintentional.
2. Not paying attention or considering.

Origin:

From in- ("not") + advertent, from latin advertere ("to turn toward.s")

Examples:

1. He made an inadvertent mistake.
2. The company's failure was due to an inadvertent oversight.
3. She made an inadvertent error in her calculations.
4. His comment was inadvertent and he didn't mean to offend anyone.
5. The mistake was inadvertent and not intentional.