When prefixed noun contains two syllables, use the hyphen: e.g., bucket-shop, twenty-fold, ante-room, mason-work, paper-mill, etc.[9]
When prefixed noun contains three or more syllables write as two separate words: e.g., policy shop.
6. In compounds of bi, tri, semi, or demi: e.g., bimonthly, tricolor, semiannual, demijohn. Exceptions: long or unusual formations: e.g., bi-centennial, etc.
7. In today,[10] tonight, tomorrow, viewpoint, or standpoint.
[10] Cf. the old English words to-morn, to-year, etc.
8. In connection with the negative prefixes un, in, and a: e.g., unrepublican, inanimate, etc., but the prefix non requires the hyphen except in words which have become common: e.g., non-conductor, but nonsense.
9. In connection with the words over and under employed as prefixes: e.g., overestimate, undersecretary; but over-soul, over-spiritual, under-man.
10. In connection with the Latin prepositions ante, anti, inter, intra, post, sub, and super: e.g., antedate, antidote, subtitle, etc.; but ante-room, anti-imperialistic, intra-atomic. {51}
11. In spelling out a series of fractions: e.g., I can secure you one, two, or three fifths, not one-, two-, or three-fifths.