Markush Doctrine Law and Legal Definition

Markush doctrine is principle applicable to Patent laws which permits a claimant to use an alternative, subgeneric phrase when there is no applicable, commonly accepted generic expression. It is an exception to the policy against using alternative language in claims. Generally a claimant cannot use the specific alternative phrase but can use a generic phrase that would cover effectively the desired alternatives. For example, instead of specific alternative phrase like ‘glass or plastic’ a generic phrase like ‘impervious transparent material’ can be used. However according to the doctrine a claimant can use phrase like "selected from the group consisting of A, B and C." It originally used with organic chemical compounds as there were no suitable phrase to cover the alternatives. The term Markush comes from Dr. Eugene A. Markush, who was granted a dye-preparation patent in 1923.