This is among the oldest unsolved problems in universal algebra.
Being a special instance of lattices, they are studied both in order theory and universal algebra.
Furthermore, closure operators are important in the study of universal algebra.
The universal enveloping algebra is a way to grasp all such properties and only them.
Some related results of universal algebra are the following.
Nevertheless model theory can be seen as an extension of universal algebra.
All the above cases may be unified and generalized in universal algebra.
The study of varieties is an important part of universal algebra.
Many standard results in universal algebra hold only for varieties.
Nelson made contributions to the area of universal algebra with applications to theoretical computer science.