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.
The metric unit prefixes are short words that indicate a multiple or fraction of a unit. The prefixes are the same no matter what the unit is, so decimeter means 1/10th of a meter and deciliter means 1/10th of a liter, while kilogram means 1000 grams and kilometer means 1000 meters. Decimal-based prefixes have been used in all forms of the metric system, dating back to the 1790s.