Definition 0.1. A category 𝒞1 with coproducts is called a C1-category if for every family of of monomorphisms the morphism
is also a monomorphism ([1]).
Remark 0.1. With certain additional conditions (as explained in ref. [1]) 𝒞1 may satisfy the Grothendieck axiom 𝒜b5, thus becoming a C3-category (Ch. 11 in [1]).
[1] See p.81 in ref. [266] in the Bibliography for categories and algebraic topology
[2] Ref. [288] in the Bibliography for categories and algebraic topology