Are there any rules when to write a set of two (or more) words or abbreviations forming a name of some entity as separate, when to hyphenate, and when to stick them together?
These are my findings with ngram:
- bitwise, bit-wise, but never bit wise
- sci-fi, but never sci fi, or scifi
- wastelands (increasingly frequent), waste lands (dying out), never waste-lands
- fanfiction or fan fiction, but almost never fan-fiction, but
- fanfic, never fan fic or fan-fic
- read-only or read only, rarely readonly
- twofold (frequently), two-fold (rarely), two fold (minimal)
- bittersweet (rise), bitter-sweet (decline), bitter sweet (minimal), but...
- sour-sweet (frequent), sour sweet (less frequent), soursweet (even less frequent)
- all-nighter (dominant), allnighter (infrequent), all nighter (somewhat less frequent)
- cross-country (gaining), crosscountry and cross country (about equal, not infrequent)
- overnight (rise), over night (same as overnight until 1920, then drops to 0), very rare over-night.
In particular, if I'm coining a new blend, which rules should I follow when deciding which of these three forms to give it?