In everyday life, there is very little difference between the two words and as such they are used interchangeably. However in some specialized fields, there are differences. For example in Law (under law of contract), there is an established difference. There is a legal maxim in law of contract that states that "Consideration needs not be adequate but must be sufficient" This maxim clearly establishes difference in both words (though similar). Adequacy is more exact in nature that sufficiency. This means something is adequate if its exactly equal to requirement whereas sufficiency means something is within a relevant range of the requirement.