Etymology

Old English has los "loss, destruction," from a Proto-Germanic root *lausam- (see lose), but the modern word probably evolved in the 14th century from lost, the original past participle of lose, itself from losian "be lost, perish," from los "destruction, loss", from a Proto-Germanic root *lausa (cf. O.N. los "the breaking up of an army"), from Proto-Indo-Eeuopean base *leu- "to loosen, divide, cut apart, untie, separate"

Noun

1. An instance of losing, such as a defeat

   The match ended in their first loss of the season.

2. Something that is lost

   It was written off as a loss.

3. The hurtful condition of having lost something or someone

   We mourn his loss.

4. (plural) Casualties, especially physically eliminated victims of violent conflict

   The battle was won, but losses were great.

5. (financial) The sum an entity loses on balance.
6. The sum of expenditures and taxes minus total income is a loss, when this difference is positive.
7. Destruction, ruin

   It was a terrible crash: both cars were total losses

8. Elecrical of kinetic power expended without doing useful work.

   The inefficency of many old-fashioned power plants exceeds 60% loss before the subsequent losses during transport over the grid

Usage notes

• We often use make or take a loss. See Appendix:Collocations of do, have, make, and take