Final answer:
The abbreviation IU stands for International Unit, not 'intravenous'. It is a measure of biological activity used for substances like vitamins and vaccines, and is distinct from SI units like grams or moles.
Step-by-step explanation:
The abbreviation IU stands for International Unit and is commonly mistaken for 'intravenous,' which is not correct. IU is a unit of measurement for the potency of a substance based on its biological effect or activity. It's particularly used in the context of vitamins, hormones, some medications, vaccines, blood products, and similar biologically active substances. The International System of Units (SI) is a different system of measurement that does not use the IU; instead, it uses units like grams and moles for mass and concentration, respectively. Mistaking IU for 'intravenous' could lead to confusion, especially within medical settings where precise terminology is crucial for treatment and dosing.