Constant and earnest effort to accomplish what is undertaken; persistent exertion of body and mind. (Dictionary.com)
Law. The degree of care and caution required by the circumstances of a person. (Dictionary.com)
Steady, earnest, and energetic effort : persevering application: assiduity. (Merriam – Webster)
The attention and care legally expected or required of a person (such as a party to a contract) (Merriam – Webster)
The quality of working carefully and with a lot of effort. (Cambridge Dictionary)
Careful and persistent work or effort. (Oxford Dictionaries)
Four Ways Diligence Can Make Your Work Easier and More Rewarding.
Diligence – Importance of Diligence in your personal and professional life.