Not “there isn’t enough.” A relationship: wants keep expanding faster than the means available to meet them.
In the discipline-defining formulation economist Lionel Robbins gave in 1932, economics is “the science which studies human behaviour as a relationship between ends and scarce means which have alternative uses.” Scarcity isn’t a temporary shortage to be fixed — it’s the permanent condition the field is built to study, because human wants are treated as effectively unlimited while any given means (time, money, land, labour) is not.
Treating scarcity as fixed and given, rather than as one lens among others, has consequences: it frames choice primarily as competition over a limited pool, and it can make voluntarily limiting one’s own wants look irrational rather than like a live alternative response to the same underlying condition.
Source: Robbins, L., An Essay on the Nature and Significance of Economic Science, Macmillan, 1932.