expression
first in; putting in first
Used when something is placed, inserted, or added before other items, often in contexts like loading, filling, or queuing.
洗濯機に洗剤を先入れしてから衣類を入れてください。
Please put the detergent in the washing machine first, then add the clothes.
この機械は材料を先入れする必要がある。
This machine requires the materials to be loaded first.