What's the difference between maintenance, upkeep & sustenance?

Answer 1

Maintenance and upkeep are similar words, as I'm sure you've noticed, they appear in each other's synonym entries as service, repair, improvement, etc. Auf Deutsch: Unterhalt, Wartung, etc. Upkeep maybe is used more often in connotation with houses or vehicles/physical machines (eg: "the upkeep on this yacht is very expensive"), while maintenance is way more general (maintenance could be done to an operating system on a computer for example, where I would not say "upkeep" on a computer system), but these 2 words are in essence very similar and interchangeable. Maintenance can also be used as a standalone noun meaning the people who service a building or institution. So you could say "you should call Maintenance about this problem" when your sink starts to leak.

Sustenance is a slightly different concept. Sustenance typically means food (or drink, or anything else essential to keeping a body alive.) Synonyms: nourishment, rations, etc. Sustenance does have a second entry in the dictionary saying support or maintenance, but this is more unusual. In this case (example sentence, "he kept livestock for the sustenance of his family", it means that the livestock was kept literally to feed the family.) So yes, you might find these 3 words grouped together in some synonym dictionaries, but sustenance has a very strong relation to food specifically. Maintenance and upkeep are more general (and could refer to anything from money to mechanical issues) and maintenance by far is the most general in terms of acceptable usage.