The primary difference between a townhome and a duplex is that a duplex is a property that holds two separate single-family residences, whereas a townhome is a single-family residence built in a row of homes. Duplex residences normally sit side-by-side, while townhomes are typically narrow and tall.
The residences in a duplex are both encompassed within a single building. Townhomes are normally built in a row, but each townhome may have its own garage and front entrance. Both property types have historically been uniform in style. However, in 2014, townhomes in a subdivision or community are increasingly distinct in style.