a. [f. late L. agentia, or L. agenti- stem of agens (see AGENT a.) + -AL; cf. essential, prudential.] Of or pertaining to an agent or agency.
1872. F. Hall, False Philol., 65. Of the same class with them [‘tangential’ and ‘exponential’] is ‘agential,’ a word of prime utility, as referring, indifferently, to ‘agent’ and to ‘agency.’ Ibid., 60. To obtain an agential substantive complementing the verb photograph.
