Function
Assessing the 'Function' of a product involves more of an element of the performance than does considering the purpose behind its creation.  An item can be said to be 'functional' if it capable of doing the task for which it was designed - that is fulfilling the purpose behind its design.
The 1940's saw a series of 'functionalist designs' - This was a time when consumers had little income that could be given over to acquiring products that did more than satisfy the need for which they were designed.    After all it is a bonus if a table or a chair looks good and feels good.  If it merely performs the function of supporting objects at a suitable height (say for writing, reading or eating meals) then a table is functional and its cost might be expected to be less than something made of exotic and expensive materials.