H [Greek symbol alpha]—hydrogen-alpha; either abbreviate both words or spell both out. Do the same for hydrogen-beta and hydrogen-gamma.
hailfall—one word, by analogy with rainfall
headings—Create a style sheet for each unique print document. For online content, sentence style has been preferred by UCAR Communications since 2010. A heading that includes a colon takes an initial cap after the colon. Example: Zooming in: Winter beauty. [02/2012]
humidiometer—synonym for hygrometer, equally common
HYPERchannel—a high-speed digital communications system manufactured by Network Systems Corporation. Spell this way.
hyphen—Use for phone numbers, document section numbers, and other analogous situations.
Do not break words so that
one letter is left at the end of a line or two letters appear at the beginning of a line (a-cross and flamin-go are unacceptable hyphenations, even though the words are broken into syllables correctly)
what looks like an unrelated word is left at the end of a line (pet-ulant is an unfortunate hyphenation).
Avoid half-word widows at the end of a paragraph if they are shorter than the paragraph indent.
In layout, do not end a right-hand page with a hyphenated line.
If a sentence contains an em dash that falls at a line break, put the dash at the end of one line, not at the beginning of the next.
See also "line breaks".