intra (in-tr<<schwa>>), adv. & adj.[Latin] Within. Cf. INFRA.

“The use of infra (below) in the sense and place of intra (within) is a corruption of very ancient date…. The expression ‘under age’ (the correct literal translation of infra aetatem) indeed, is of more common occurrence than ‘within age.’ But the use of infra in the sense of intra, as expressive of place, is an undoubted barbarism.” 2 Alexander M. Burrill, A Law Dictionary and Glossary 75 (2d ed. 1867).

[Blacks Law 8th]