Inflammation
Etymology
From Latin inflammare, "to set on fire," from in-, "into," and flamma, "flame." The name captures how it feels and looks: a spot that is hot, red, and burning. Acute inflammation is the immune system rushing to repair damage. When it persists as low-grade, long-term inflammation, though, that same protective fire can quietly wear the body down.
noun · /in-fluh-MAY-shun/
The body’s protective response to injury or infection — redness, heat, swelling, and pain as it mobilizes to heal.
What it names
A defense that is helpful in short bursts but harmful when it lingers — the reason "chronic inflammation" turns up in so much health writing.
Example
Ice reduced the inflammation around the sprained ankle within a day.
Related idea
Inflammation is often acute and healing, but when it turns chronic it can do harm instead.