Question

According IUPAC, how are root words assigned?

Answer 1

root words are assigned according to the number of carbon atoms in the carbon skeleton

Explanation:

source:http://www.tutorvista.com/content/chemistry/chemistry-iii/organic-chemistry/aliphatic-compounds.php

i actually wanted to show you the first 2 columns of the above table. the root name is assigned according to the number of C atoms. the typical alkane names are given in the graph.
when you are naming compounds you can name them accordingly by adding suffixes and prefixes to the root name.