Single source publishing, also known as single sourcing, allows the same content to be used in different documents (deliverables) or in various formats. The labour-intensive and expensive work of editing need only be carried out once, on one document. Further transformations are carried out mechanistically, by automated tools. You may also add new output formats in the future, as your organization's needs change.
Single Sourcing also refers to the act of one single source (vender) being chosen to do business with for a product. This is when one single supplier is awarded to supply the good or service because they are a very specialized company or have unique characteristics to what they supply and offer. The customer would purchase from one supplier, opposed to multiple suppliers.