Other forms: regained, regaining, regains
To regain something is to get back what you had lost. It was yours, it went, and now it is yours again.
It suits abstractions above all: regain consciousness, regain control, regain your balance, regain the lead. Those are close to fixed phrases, and regaining consciousness is the standard medical wording. It is more formal than get back and more precise, since regaining implies returning to a former state rather than simply acquiring. There is no noun regain, so recovery does that work instead.
1verbregainTo get back something previously lost.
“He never fully regained the use of his hand.”
Middle French
regaigner
English, today
regain
From Middle French regaigner (French regagner). by surface analysis, re- + gain.
Etymology from Wiktionary, CC BY-SA