94. Hyphenation

Wed Feb 08, 2023 2:19 pm

age terms
a three- year- old

colors
emerald- green tie
reddish- brown flagstone

compass points and directions
a north–south street

fractions, compounds formed with
a half hour
a half-hour session
a quarter mile
a quarter-mile run

fractions simple
one-half
two-thirds

number + noun
a hundred-meter race
a 250-page book

number, ordinal, + noun
third-floor apartment
103rd-floor view
fifth-place contestant
twenty- first-row seats

number, ordinal, + superlative
a second-best decision
third-largest town
fourth-to-last contestant

numbers, spelled out
twenty-eight
three hundred
nineteen forty-five
five hundred fifty

More here (complete):
ophi.org.uk/wp-content/uploads/CMS_list.pdf

According to Chicago Manual, we need to hyphenate least-thought and least-understood. According to the Chicago Manual of Style, compounds with well, ill, better, best, little, lesser, and least, are hyphenated before the noun (well-deserved award), not hyphenated after a noun (the award was well deserved), and not hyphenated when modified by an adverb (very well deserved award).