@[email protected] reactions, in which processes like \[\text{A}\ \overset{1}{\rightarrow }\ \text{Y}\] and \[\text{B}\ \overset{2}{\rightarrow }\ \text{Z}\] occur in parallel, can be called simultaneous or @[email protected] Sometimes there is @[email protected] involved, like in the scheme: \[\text{A}\,+\,\text{B}\ \overset{1}{\rightarrow }\ \text{Y}\] and \[\text{A}\,+\,\text{C}\ \overset{2}{\rightarrow }\ \text{Z}\] where B and C compete with one another for A.