Estates in real property, in respect to the duration of their enjoyment are:

1. (1) Estates of inheritance or perpetual estates;
2. (2) Estates for life;
3. (3) Estates for years; or
4. (4) Estates at will.

Source: CivC 1877, § 218; CL 1887, § 2734; RCivC 1903, § 241; RC 1919, § 311; SDC 1939, § 51.0402.