What is the relationship of a kilocalorie and a calorie?

As far as I know, they are the same thing. Either that or a calorie is infinitesimal. Kilocalories are what most refer to simply as calories (the calories listed on food labels.)

Answer

The clue is in the prefix, 'kilo'. A kilocalorie (kcal) is one-thousand calories (cal). The problem is that people in the food industry are either simply too lazy or too stupid to use the work 'kilocalorie'.

As the calorie is an obsolete unit, they should be using the joule.