第一线 (dì yī xiàn) — forefront, front line; the most crucial part (of an operation, project, etc.)

Definition

Examples

• 战士们冲到了第一线。
  Zhàn shì men chōng dào le dì yī xiàn.
  The soldiers rushed to the front line.
• 他始终站在科研的第一线。
  Tā shǐ zhōng zhàn zài kē yán de dì yī xiàn.
  He always stands at the forefront of scientific research.
• 这个问题是谈判的第一线。
  Zhè ge wèn tí shì tán pàn de dì yī xiàn.
  This issue is the most crucial part of the negotiation.