Root words are the smallest part of a word without a beginning or ending on it. Thousands of words have root words, I'm sure you can find lots of examples if you just look around for inspiration.
It depends on who the owner is. Has is part of the French verb "Avoir" (to have) which is irregular so how you say it depends on the number of people, and the gender you are talking about (just like in English). I (ai) you (a) he/she (a) We (avons) You (plural) (avez) They (ont)