In linking a subordinate clause and a main clause, a relative pronoun functions similarly to a subordinating conjunction. Unlike a conjunction, however, a relative pronoun does not simply mark the subordinate (relative) clause, but also plays the role of a noun within that clause.
The main ingredient in most vodkas is some kind of grain, such as wheat, corn or rye. Potatoes are another common base ingredient for vodka, according to About.com.
Vodka Collins recipe. Shake vodka, lemon juice and powdered sugar with ice and strain into a collins glass. Add several ice cubes, fill with carbonated water, and stir. Garnish with slices of orange and lemon, and top with a cherry. Serve with a straw.