- commands for the engine, as a string, or a sequence or list of strings, which cause a ring to be placed on the top of the engine's stack.
- a ring, in which case another top-level ring is formed as an interface to the same underlying engine ring.
- the handle of on engine ring

- FractionField -- the class of all fraction fields
- GaloisField -- the class of all Galois fields
- InexactField -- the class of inexact fields
- PolynomialRing -- the class of all ordered monoid rings
- QuotientRing -- the class of all quotient rings

- frac(EngineRing) -- see frac -- construct a fraction field
- isField(EngineRing) -- see isField -- whether something is a field
- numgens(EngineRing) -- see numgens(Ring) -- number of generators of a polynomial ring

The object EngineRing is a type, with ancestor classes Ring < Type < MutableHashTable < HashTable < Thing.