| 08A02 | Relational systems, laws of composition |
| 08A05 | Structure theory |
| 08A30 | Subalgebras, congruence relations |
| 08A35 | Automorphisms, endomorphisms |
| 08A40 | Operations, polynomials, primal algebras |
| 08A45 | Equational compactness |
| 08A50 | Word problems [See also 03D40, 06B25, 20F10, 68R15] |
| 08A55 | Partial algebras |
| 08A60 | Unary algebras |
| 08A62 | Finitary algebras |
| 08A65 | Infinitary algebras |
| 08A68 | Heterogeneous algebras |
| 08A70 | Applications of universal algebra in computer science |
| 08A72 | Fuzzy algebraic structures |
| 08A99 | None of the above, but in this section |