Deprecate means to express disapproval of something or to officially phase it out (a deprecated feature still works, but you are told to stop using it). Depreciate means to fall, or be lowered, in value, as with a car that depreciates each year. Remember: depreciate is about price, deprecate is about disapproval.
The core difference
Deprecate is about disapproval or phasing something out; depreciate is about a drop in value.
- deprecate — to declare something obsolescent or to voice disapproval: The old login method was deprecated in favour of the new one.
- depreciate — to lessen in price or decline in value over time: A new car depreciates fast in its first year.
How to tell them apart
Both words trace back to Latin roots built on precor, "to pray", and pretium, "price" — close cousins that drifted apart in meaning. Deprecate keeps the sense of pleading or disapproving, which is how it came to mean "recommended against" in software, where a deprecated command still works but is on its way out. Depreciate keeps the sense of price, so it belongs with money, assets and value.
The mix-up shows up most in tech writing and finance copy, where a feature can be "deprecated" but only an asset can be "depreciated". If you can swap in "lost value", you want depreciate; if you can swap in "phased out" or "disapproved of", you want deprecate.
