Salary is a form of periodic payment specified in an employment contract.
While 'wage' and 'salary' are often used interchangeably, 'salary' refers in particular to payment associated with a position over a fixed period of time, such as per week, per month, or per year. A manager or other person with oversight responsibilities (commonly referred to as a 'white-collar worker') would be more likely to draw a salary. A labourer or 'blue-collar worker' would take wages (usually paid weekly, biweekly, or monthly), based upon the actual hours worked.
Etymology
'Salary' derives from the Latin words sal meaning salt and salarium, a payment made in salt. In medieval times salt was a valuable barter commodity. (also the proverb 'to be worth one's salt').
History
Pliny following Aristotle's ideas, interpretes the use of salt as a means of payment: ". . . in Rome . . . the soldier's pay was originally salt and the word salary derives from it . . . " Plinius Naturalis Historia. XXXI -
However we should note that Pliny may well have interpreted this payment wrongly. To judge from the missions and the locations to which the Roman army was despatched, it would seem that protecting the salt sources and ensuring the viability of the 'via salarium' was the true military objective - The first "legions" aka : LEGIO : "levying" were for the monarchy
External link:The Salt Archive Economics
SALT Archive