Reasonable

Agreeable to reason; conformable to law; ordinary or usual. Reasonable care: the care which men of ordinary prudence are accustomed to employ, v. Ordinary. Reasonable cause: as applied to human action, that which would constrain a person of average intelligence and ordinary prudence; probable cause; legal cause. Reasonable doubt: as applied to jurors, a condition of mind, after consideration and comparison of all the evidence, short of an abiding conviction to a moral certainty of the truth of the charge. Reasonable skill: as applied to a physician or surgeon, the skill commonly possessed and employed by men of the profession. Reasonable time: depends on the circumstances of the case.

In old English law

Reasonable part: the share of the goods of a man which the law gave to his wife and children upon his decease.