How do you get rootword?

Answer 1

Most comprehensive dictionaries will give the root of a word. In English, commonly from the older languages of Greece or Latin, but with liberal dashes from other continental languages. English is notorious for borrowing words from anywhere convenient. e.g. Chlorophyll; chlor ~ green and phyllum ~ leaf, both from Greek.

You should not expect such a level of detail in a 'concise' or a 'student' dictionary, whose main purpose is to provide a spelling check.