What is difference between convectional current and conduction current?

Conduction refers to electrons or, "holes" in the case of semiconductors, which are conducted, under the influence of an electric field, from one place to another. However, in semiconductor there is a phenomenon called "drift current" which is more a function of very small field and random motion from one place, within the material, to another place. But neither of these is ever referred to as a "convection" current. The term "convection" is used in connection with air currents moved by differences in temperature between one place and another. Hot air tends to rise while cold air tends to fall. Consequently, a circulation of air, due to temperature is called a convection current.