ichidan verb, transitive verb
pile up; heap up; stack; lay (bricks)
Physical action of stacking objects or materials into a pile. Often used for bricks, boxes, books, sand, etc.
子供たちは砂場で砂を積み上げて山を作った。
The children piled up sand in the sandbox and made a mountain.
He neatly stacked bricks and built a wall.
ichidan verb, transitive verb
accumulate; build up; amass
Abstract use: gradually gaining experience, achievements, trust, reputation, etc. Often used with words like 経験, 実績, 信頼.
彼は長年の努力で信頼を積み上げてきた。
He has built up trust through years of effort.
若いうちに多くの経験を積み上げることが大切だ。
It is important to accumulate a lot of experience while you are young.