A dark róom (phrase) is any room that is dark, but a dárk room (compound word) is where photographers work, and a darkroom can be lit when the photographer is done. A black bóard, (phrase) is necessarily a board that is black, but some bláckboards (compound word) are green or even white. Without pronunciation or punctuation as a guide, some word strings can be read either as a phrase or as a compound, like the following headlines:
