@jinmin1988,
jinmin1988 wrote:
The line chart illustrates the global water used by agriculture, industry and households over the nineteenth century.
Which word is more idiomatic in this sentence:household or family? Should it be plural form or single?
Thank you.
A "household" may contain more than one family (depending on the definitions of family and household that you use), so I don't think the terms are necessarily interchangeable, depending on the level of accuracy you are trying to achieve. In non-clinical communication the terms might be interchangeable.
If the sentence was in relation to a scientific study, then "household" would probably be the more accurate term if the study dealt with dwellings instead of familial relationships.