How do you treat the word size (or is it sized?) when it’s used in combination with other words as an adjective? Here’s a rundown of the options, with judgments about the best bets.
The combination of mid with size is treated in various combinations: as midsize, mid-size, midsized, and mid-sized. The most prevalent form, logically — following the tendency to omit hyphens after prefixes and because omitting the second d is simpler than retaining it — is midsize. Medium-sized, however, prevails over medium-size; the hyphen is to be expected, because medium is an entire word, not just a prefix, like mid, but the retention of the final d is puzzling.
Midsize is the adjective of choice for vehicles, while medium-sized is much more likely to apply not only to entities such as businesses and organizations but also to most other products and objects.
And how should references to comparatively small or large phenomena be styled? Some people would follow the pattern by writing small-size or small-sized, or large-size or large-sized, but -size or -sized is redundant because small and large provide a frame of reference to the quality being discussed, whereas medium is vague enough to require the contextual clue of -sized, even when small and/or large are also employed in the passage. (A range should be rendered as follows: “Small to midsize cars were tested” or “The survey applied to small to medium-sized businesses.”)
Words for bed sizes are expressed as, for example, king-size or king-sized. Merriam-Webster’s Collegiate Dictionary, probably the most widely consulted dictionary in the publishing industry, notes that king-size is prevalent, which is consistent with its entries for similarly constructed words, include bite-size, legal-size, life-size, man-size, plus-size, pocket-size, in which the -sized form is regarded as a variant.
Similar terms, such as those in the sentences as “We watched a car-size boulder tumbling down the slope” or “A house-size depression appeared in the field,” can be created as needed. However, writers should take care in producing such constructions with less common references. “He approached the brick-size object as it hovered in front of him” is reasonable, because although bricks vary in size, most readers will probably think of the typical red clay building material. But “a dog-size creature” is vague because of the disparity of size among dog breeds, and “a cell phone–size device” may seem awkwardly constructed. (Try “a device the size of a cell phone” instead.)