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▹
Category theory
▹
Concrete categories
Definition 4.9.6.
Let
u
∈
ℕ
. We define:
SemiGrp
u
:
=
[
SemiGrp
(Hom(
A
,
B
))
A
,
B
∈
SemiGrp
(id
C
)
C
∈
SemiGrp
(∘)
D
,
E
,
F
∈
SemiGrp
]
u
is a/an
u
-small category
Remarks.
The objects of this category are actually isomorphism classes of semigroups.