Upside-down and Upside down

Upside-down adjective - Lacking in order, neatness, and often cleanliness.

Upside down and upside-down are semantically related In some cases you can replace phrase "Upside down" with "Upside-down", this phrases are similar.

Upside down adverb - In an inverted manner.

Upside-down and upside down are semantically related in reversed topic. You can use "Upside-down" instead the phrase "Upside down" as an adjective or an adverb.