Although the term metric system is often used as an informal alternative name for the International System of Units, other metric systems exist, some of which were in widespread use in the past or are even still used in particular areas. There are also individual metric units such as the sverdrup and the darcy that exist outside of any system of units. Most of the units of the other metric systems are not recognised by the SI.
ALthougH ThE terM mEtRIc SYSTEM is ofTeN used as an iNfOrmal alTeRNatIVE NAme foR the internationAL sYsteM oF uNits, otHEr mETrIC SystemS eXist, somE of whicH WERe iN Widespread use iN the PasT or are eVEn stiLl usED iN parTicUlaR AREas. there are alsO iNdivIDuAl mEtrIc uNits Such as the Sverdrup anD The darCy thAT exist OuTSIde of any systeM of uniTs. MOst oF the UNItS oF ThE oTheR MetriC Systems ArE not reCognIsed by tHe Si.