Of all the types of value that can be appraised, this is the type of value that is the major focus for most real property appraisals.  There have been several definitions for this established by various organizations operating within the appraisal industry, but one of the most common, that is utilized in virtually all mortgage lending transactions, is the following:
Definition of Market Value
Market value is the most probable price that a property should bring in a competitive and open market under all conditions requisite to a fair sale, the buyer and seller, each acting prudently, knowledgeably and assuming the price is not affected by undue stimulus. Implicit in this definition is the consummation of a sale as of a specified date and the passing of title from seller to buyer under conditions whereby:
buyer and seller are typically motivated;
both parties are well informed or well advised, and each acting in what he or she considers his/her own best interest;
a reasonable time is allowed for exposure in the open market;
payment is made in terms of cash in U.S. dollars or in terms of financial arrangements comparable thereto; and
the price represents the normal consideration for the property sold unaffected by special or creative financing or sales concessions granted by anyone associated with the sale.
Source: B4-1.1-01, Definition of Market Value (04/15/2014) (fanniemae.com)