Marginal
Part of speech: noun
Definition: Something that is marginal. Especially a constituency with a small winning margin.
Part of speech: adjective
Definition: of, relating to, or located at a margin or an edge geographically adjacent written in the margin of a book at the lower extent of a standard of land that is barely productive of an electoral district (such as a parliamentary constituency) where the winning margin was a small proportion of the total number of votes, so that only a small change in voting behaviour is necessary to alter the outcome of an election.
Example sentence: Keynesian modelling relies on marginal propensity to consume and marginal propensity to invest. The idea that if we give more money to the poor, they have a propensity to consume that's much higher than the wealthy, though I wish they would talk to my wife about that; she seems to have a propensity to consume.
Unprofitable
Part of speech: adjective
Definition: Not making a profit.