Complex sentence: The sievert (symbol: Sv) is the International System of Units' (SI) derived unit of ionizing radiation dose and is a measure of the effect of low to moderate levels of radiation on the human body.
Split into simpler sentences: The sievert (symbol: Sv) is the derived unit of ionizing radiation dose in the International System of Units. It is a measure of the effect of low levels of radiation on the human body.