simultaneous reactions

Composite reactions, in which processes like

$A → 1 Y$

and

$B → 2 Z$

occur in parallel, can be called simultaneous or parallel reactions. Sometimes there is competition involved, like in the scheme:

$A + B → 1 Y$

and

$A + C → 2 Z$

where B and C compete with one another for A.

Source:

PAC, 1993, 65, 2291 (Nomenclature of kinetic methods of analysis (IUPAC Recommendations 1993)) on page 2297