The term refers to the people being able to afford it. If, in Denver, the available housing is priced higher than what many sectors of the Denver market can afford to pay then there is a lack of housing affordable to them (teachers, nurses, firefighters, police, etc.) If for example the lowest priced house in Denver is priced at $300,000, then there is a lack of affordable housing for many in the workforce.

This is one of the reasons you can't drive anywhere in metro Denver within 30 minutes any more like we could in the '70s. Working families more and more need to move outward to find affordable housing.