LXVIII. As a rule, a hyphen should not be placed after a simple prefix: "contravene," "preternatural," "hypercritical," "bilateral."
To this there are some exceptions:
(a) "Anti-religious," "ultra-liberal," "semi-lunar," "co-eval." In these words the pronunciation is more clearly marked by inserting the hyphen. Compare "antiseptic," "antinomian," "ultramontane," "semicircle."
Perhaps among these exceptions should also be included such words as "pseudo-critic," "non-ego," "non-existent." Compare "pseudonym," where the prefix is contracted, and "nonentity." Words like "pre-eminent," divided for the same reason, have already been noted.
(b) "Re-creation," "re-mark." The hyphen distinguishes the etymological meaning of these words as distinguished from their derived and ordinary meaning.
(c) "Pre-Norman," "anti-Darwinian," "philo-Turk." If the capital-letter be retained where a prefix is put to a proper name, the hyphen is obviously necessary.
LXIX. When a number is written in words and not in figures, the words making up the number, if there be more words than one, are in certain cases separated from each other by the hyphen.
The numbers to which this rule applies are the cardinal and the ordinal numbers from twenty-one and twenty-first to ninety-nine and ninety-ninth inclusive. The hyphen is used also when the words are inverted; as "four-and-thirty," "six-and-fortieth."
LXX. Fractional parts written in words are separated in the same way, a hyphen being placed between the numerator and denominator; as "two-thirds," "three-sixteenths."
But if the word "part" or the word "share" follows, the hyphen is not used; as "two third parts."