Compute the ratio of the object's height to its weight. What is the car's power to weight ratio? The staff to student ratio has increased dramatically in the last five years. The efficiency of a machine is the ratio between the energy it supplies and the energy put into it. Pi is the ratio of a circle's circumference to its diameter. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.