Loss is the noun, lose is the verb — you lose something, and afterwards you feel the loss. A quick memory hook: lose rhymes with choose and describes an action you do, while loss rhymes with cross and names a thing or a state.
The core difference
Loss is a noun naming the state of no longer having something, while lose is the verb describing the act of losing it.
- loss (noun) — the state of no longer having something: The loss of his phone meant he had no way to contact anyone.
- lose (verb) — to no longer have something, or to fail to win: She lost her keys somewhere between the car and the front door.
How to tell them apart
The mix-up usually comes down to spelling rather than meaning, since most people already know the difference between the two ideas. Loss has two letter O's and one S at the end, and it works the way words like cost or loss of income do — it names a thing. Lose has one O, and it works the way words like choose or use do — it names an action someone does.
A simple test: if you can put 'the' in front of the word, you probably want loss (the loss, a loss). If you can put 'to' or 'will' in front of it, you want lose (to lose, will lose). Both words also stretch beyond possessions: loss covers defeat in a game and the grief of bereavement, while lose covers failing to win and losing your way or your train of thought.
