Lubrication; smoothness — reducing friction so things move smoothly; also used figuratively for smooth progress (e.g., negotiations).
機械の潤滑が不十分だと、部品が早く摩耗する。
If the machine's lubrication is insufficient, parts wear out quickly.
両国は貿易協議を潤滑に進めるために専門家を派遣した。
The two countries dispatched experts to facilitate smooth progress of trade talks.
潤滑油を定期的に交換することが重要だ。
It's important to change the lubricant regularly.