Complex sentence: For multiples of the tonne, it is more usual to speak of millions of tonnes; kilotonne, megatonne, and gigatonne are more usually used for the energy of nuclear explosions and other events and are often used loosely as approximate figures.
Split into simpler sentences: For multiples of the tonne, it is more usual to speak of thousands or millions of tonnes. Kilotonne, megatonne, and gigatonne are more usually used for the energy of nuclear explosions and other events, often loosely as approximate figures.