A multifamily dwelling is one that contains three or more dwelling units [Art. 100]. Though similar, single and multifamily dwellings have distinct differences.
The wiring method used for a single-family dwelling unit is often Type NM cable (unless local codes don’t allow it). Depending on factors such as the building construction type and local codes, a multifamily dwelling may require the use of metal raceways or metallic-sheathed cable [334.10, Annex D].