An agreement or arrangement between an employer or employers' association and one or more trade union. Such an agreement may cover terms and conditions of employment and conditions of work; hiring, firing and suspension; allocation of work; discipline; union membership; union recognition; facilities agreements; procedures and the other machinery of collective bargaining. It is not legally binding as between the parties unless in writing and stated to be so, although it may have binding consequences as between a worker and an employer if it is incorporated into the worker's contract. Many of the statutory consequences depend upon the collective agreement being in writing. But an agreement may be a collective agreement whether it is formal or informal, whether it is written or oral, whether indeed it is an agreement or merely an arrangement.