The root word used for 8 carbons in parent chain is
Oct
The word roots used for the number of carbon atoms present in the principal chain of the molecule are:
Chain lengthRoot WordChain lengthRoot WordC1MethC11UndecC2EthC12DodecC3propC13TridecC4ButC14TetradecC5pentC20IcosC6HexC30TriacontC7HeptC40TetracontC8OctC50PentacontC9NonC60HexacontC10Dec