第一線

(1)the position of greatest importance or advancement; the leading position in any movement or field; "the Cotswolds were once at the forefront of woollen manufacturing in England"; "the idea of motion was always to the forefront of his mind and central to his philosophy"

(2)最も大きな重要性または進歩の状況

(3)あらゆる運動または分野での指導的地位

(4)a fortified position (especially one marking the most forward position of troops); "they attacked the enemy's line"

(5)要塞化された場所（特に軍隊の一番前の場所を指す）

(1)