第一線(だいいっせん) だいいっせん noun the forefront; the front line workabstract 1. the forefront; the front line (of a field) The leading, most active position in a field of work. Originally the front line in war, now mostly figurative. 第一線(だいいっせん)で活躍(かつやく)する。 To be active at the forefront. 彼(かれ)は去年(きょねん)第一線(だいいっせん)を退(しりぞ)いた。 He retired from the front line last year. 七十歳(ななじゅっさい)を過(す)ぎた今(いま)も、彼女(かのじょ)は研究(けんきゅう)の第一線(だいいっせん)に立(た)ち続(つづ)けている。 Even past seventy, she remains at the forefront of research. Common collocations第一線(だいいっせん)で活躍(かつやく)する: to be active at the top of one's field第一線(だいいっせん)を退(しりぞ)く: to step back from active work第一線(だいいっせん)に立(た)つ: to stand at the forefront第一線(だいいっせん)の研究者(けんきゅうしゃ): a leading researcherSimilar words最前線(さいぜんせん): the very front line; more often literal (battle, disaster sites) or the cutting edge前線(ぜんせん): the front (in war); also a weather front Related Words Compare: 最前線(さいぜんせん) (the very front line) Compare: 前線(ぜんせん) (the front) general Added 2026.10.8 4:20 · Revised 2026.10.8 4:23 31500/31712_daiissen