Русско-англо-русский юридический словарь

Reasonable time refers to the amount of time that is fairly required to do whatever is required to be done, conveniently under the permitted circumstances.

In contracts, reasonable time refers to the time needed to do what a contract requires to be done, based on subjective circumstances. If the parties entering the contract do not fix a time for performance, the law will infer a reasonable time within which it should be done.

Under commercial law, Uniform Commercial Code UCC 2-206(2) requires that acceptance of an offer be made within a "reasonable time" if no time is specified. (definitions.uslegal.com)

Some dissonance might be perceived if lots of abstract work is described as “a large volume of work” instead, but no such dissonance will be perceived if lots of physical work is described as “a large amount of work” instead. The differences will be largely subjective, with different writers or speakers gravitating to either “amount” or “volume” as a matter of temperament or personal style. Either way, it will be needless or foolhardy to fault them for their choice of usage. (Jose Carillo's English Forum)

In criminal law, intent is a subjective state of mind that must accompany the acts of certain crimes to constitute a violation. (Wikipedia)

Each crime can be split into actus reus, the objective element of a crime, and mens rea, the mental or subjective element of the crime. (Springer)