nLab unital magmoid

Idea

Just as a groupoid is the oidification of a group and a ringoid is the oidification of a ring, a unital magmoid should be the oidification of a unital magma.

Definition

A unital magmoid $Q$ is a magmoid where every object $a \in Ob(Q)$ has an identity morphism $id_a: a \to a$, such that for any morphism $f:a \to b$, $f \circ id_a = f$, and for any morphism $g:c \to a$, $id_a \circ g = g$.

A unital magmoid is invertible if for every pair of objects $a,b \in Ob(Q)$ and for every morphism $f:a \to b$, there exists an inverse morphism $g:b \to a$ such that $f \circ g = id_b$ and $g \circ f = id_a$.

Examples

• A groupoid is a unital magmoid.

• A category and a loopoid are unital magmoids.

• A unital magmoid with only one object is called a unital magma.

• A unital magmoid enriched on truth values is a preorder.

See also

• H-spaceoid

Related concepts

algebraic structure	oidification
magma	magmoid
pointed magma with an endofunction	setoid/Bishop set
unital magma	unital magmoid
quasigroup	quasigroupoid
loop	loopoid
semigroup	semicategory
monoid	category
anti-involutive monoid	dagger category
associative quasigroup	associative quasigroupoid
group	groupoid
flexible magma	flexible magmoid
alternative magma	alternative magmoid
absorption monoid	absorption category
cancellative monoid	cancellative category
rig	CMon-enriched category
nonunital ring	Ab-enriched semicategory
nonassociative ring	Ab-enriched unital magmoid
ring	ringoid
nonassociative algebra	linear magmoid
nonassociative unital algebra	unital linear magmoid
nonunital algebra	linear semicategory
associative unital algebra	linear category
C-star algebra	C-star category
differential algebra	differential algebroid
flexible algebra	flexible linear magmoid
alternative algebra	alternative linear magmoid
Lie algebra	Lie algebroid
monoidal poset	2-poset
strict monoidal groupoid?	strict (2,1)-category
strict 2-group	strict 2-groupoid
strict monoidal category	strict 2-category
monoidal groupoid	(2,1)-category
2-group	2-groupoid/bigroupoid
monoidal category	2-category/bicategory