Unable to get the sqlcontext in Terminal in Lab

When i try to use “sqlcontext” in Sparkshell. getting following error. Please advise.
scala> val ordersDF = sqlcontext.read.json("/public/retail_db_json/orders")
:23: error: not found: value sqlcontext
val ordersDF = sqlcontext.read.json("/public/retail_db_json/orders")