bread-and-butter

Used as an adjective, bread-and-butter is hyphenated. This expression has various meanings:

• providing for the basic necessities of life
  • I hope to succeed as a writer; selling shoes is just my bread-and-butter job.
• basic; vital or essential
  • In the Speech from the Throne, the Governor General of Canada spoke of bread-and-butter issues such as jobs and housing.
• solid, dependable
  • As the highest scorer, Sarah has been the bread-and-butter player for her team this year.
  • Sales from the company’s bread-and-butter products helped it get through the recession.
• thank-you (in reference to a note or letter)
  • Mark wrote his cousins a bread-and-butter letter to thank them for their hospitality.