Unedau ychwanegol at yr Unedau SI: Gwahaniaeth rhwng fersiynau

Mae llawer iawn o unedau nad ydynt yn rhan o'r '''[[System Rhyngwladol o Unedau''']] ({{Iaith-fr|Le Système international d'unités}}; {{Iaith-en|International System of Units}}) ([[SI]])<ref>[http://www.bipm.org/en/CGPM/db/11/12/ Bureau International des Poids et Mesures]</ref> ond mae'n nhw'n cael eu derbyn ar y cyd â'r system honno.<ref>teitl="Non-SI units accepted for use with the SI, and units based on fundamental constants" [http://www.bipm.org/en/si/si_brochure/chapter4/4-1.html|accessdate=24] Mawrth 2009.</ref>