A census is a way of getting information about every member of a population. It is usually used for a population of people, but can be used to mean a population of animals. Both the United States and United Kingdom have a census every 10 years, or decade. But in Australia, Canada, Japan[1] and New Zealand they have it every 5 years.
A census produces a large database and sometimes new information technology, such as the use of punched cards for data, has been invented to handle it.
The word comes from the Roman Republic when it meant a list of citizens it was used to keep track of adult males fit for military.
Census is a word of Latin origin which means to evaluate/assess or to estimate.