Calories (mean)
A mean calorie is a unit of energy that was historically used to quantify the amount of energy required to raise the temperature of one gram of water by one degree Celsius, approximately equal to 4.184 joules.
Therm (US)
A US therm is 105,480,400 joules, which is 100,000 Btu (59°F) and roughly the energy in 100 cubic feet of natural gas. US gas bills are often given in therms.