A noun for things literally piled or stacked up, and also for the gradual accumulation of actions, effort, experience, or results over time.
The pile of books looks like it is about to fall over.
The accumulation of daily practice turned into confidence.
Success is the result of an accumulation of small efforts.
In sports, it's the day-to-day accumulation of practice that really counts.
Steady, patient accumulation of effort leads to real skill.
積み重ね emphasizes the accumulated result of repeated stacking or effort over time, while 重なり simply describes things overlapping or coinciding.
Attested mixed kana-kanji search variant; not the recommended standard spelling.
Attested search-only variant with かさね in kana; use 積み重ね in normal writing.