Syllabification: (In·ter·na·tion·al Sys·tem of U·nits)
Definition of International System of Units
a system of physical units ( SI Units) based on the meter, kilogram, second, ampere, kelvin, candela, and mole, together with a set of prefixes to indicate multiplication or division by a power of ten.
translating French Système International d'Unités
International System of Units in other Oxford dictionaries