Rigor is something strict, severe or demanding. 1  Harsh and strict treatment in the military for cadets is an example of rigor. 2  Freezing weather and ice are examples of the rigors of winter.  Difficult and challenging academic courses are an example of academic rigor.
The suffix gram means to draw or write. This is used in telegram.
1 Gram = 1000 Milligrams. Gram is a metric system unit of mass. It is one thousandth (1/1000) of the metric system base unit, kilogram. It is a very commonly used unit of mass in daily life. The abbreviation is g. Milligram is a small unit of mass in metric system and used commonly in medicine and pharmacy etc.