Complex sentence: Cable makers try to get as close to this ideal as possible and transmission lines are often assumed to have a purely real characteristic impedance in calculations, however, it is conventional to still use the term "characteristic impedance" rather than "characteristic resistance".
Split into simpler sentences: Cable makers try to get as close to this ideal as possible and transmission lines are often assumed to have a purely real characteristic impedance in calculations. However, it is conventional to still use the term "characteristic impedance" rather than "characteristic resistance".