Читать книгу The Grammar of English Grammars - Goold Brown - Страница 120

When the parts of a compound do not fully coalesce, as to-day, to-night, to-morrow; or when each retains its original accent, so that the compound has more than one, or one that is movable, as first-born, hanger-on, laughter-loving, garlic-eater, butterfly-shell, the hyphen should be inserted between them.