# 7. Non-commutative subsystem

SINGULAR has three non-commutative subsystems, handling various classes of associative non-commutative rings: PLURAL, SCA and LETTERPLACE.

> 7.1 PLURAL |  |
> 7.2 Data types (plural) |  |
> 7.3 Functions (plural) |  |
> 7.4 Mathematical background (plural) |  |
> 7.5 PLURAL libraries |  |
> 7.6 Graded commutative algebras (SCA) |  |
> 7.7 LETTERPLACE |  |
> 7.8 Functions (letterplace) |  |
> 7.9 Mathematical background (letterplace) |  |
> 7.10 LETTERPLACE libraries |  |
> 7.11 Release Notes (letterplace) |  |

User manual for Singular version 4.4.1, 2025, generated by texi2html.