Compound nouns

While compound nouns are almost always properly written as one word in Swedish, in English they may be written in three different ways: as one word, as two words, or (much more rarely) with a hyphen. For each individual compound, there is usually a preferred way to write it, which you must simply learn.

 highschool

high school

tea pot

 teapot

T shirt

 T-shirt

Note that whenever a multiple-word expression, such as a compound, is used as an adjective, all spaces must be replaced with hyphens:

an air raid siren

an air-raid siren

As an aside, do not put any spaces around hyphens. The only time you put a space after a hyphen is when there is ellipsis and the second part of the compound is left off:

The city is mostly one- and two- story houses.

The city is mostly one- and two-story houses.