Translation guide
Describes things accumulating in a heap or stack, or tasks/work building up. Japanese uses different verbs depending on what is piling up and whether the focus is on the physical heap or the accumulation of intangible things.
Describe books, dishes, laundry, snow, etc. forming a pile.
Used when objects are deliberately stacked or piled up by someone. Transitive verb 積む (to pile up) in passive/resultative form.
机の上に本がたくさん積まれている。
A lot of books are piled up on the desk.
Used for things that accumulate naturally, like snow, dust, or leaves. Intransitive verb 積もる (to pile up, accumulate).
Describe emails, homework, stress, etc. building up over time.
General term for things accumulating, often with a negative nuance of being overdue or needing attention. Used for work, stress, emails.
仕事が溜まっていて、休む暇がない。
Work has piled up and I have no time to rest.
積もる is for physical things that form a heap (snow, dust). 溜まる is for things that accumulate in a container or abstractly (water, work, stress). Using 溜まる for snow would sound odd.
雪が積もっている。
Snow is piled up.
仕事が溜まっている。
Work is piled up.
English 'be piled up' often translates to different Japanese verbs depending on what is piling up. Direct translation like パイルされている is not natural Japanese.
雪が１メートルも積もっている。
Snow is piled up as high as one meter.
Literally 'become a mountain pile'. Emphasizes a large, often disorderly heap. Common for laundry, dishes, paperwork.
洗濯物が山積みになっている。
The laundry is piled up in a mountain.
Focuses on things being stacked on top of each other, often neatly. Intransitive verb 重なる (to overlap, be piled up).
書類が机の上に重なっている。
Papers are piled up on the desk.
Emphasizes gradual accumulation layer by layer, often used for experience, achievements, or problems.
小さなミスが積み重なって大きな問題になった。
Small mistakes piled up and became a big problem.