The CLL includes a paragraph on diphthongs:
It is unclear if the paragraph defines a rule for possible diphthongs, or describes diphthongs of existing words. jbofi'e was designed so that it is applied as a rule to the lexical analysis: vlatai of it disallows cmavo to include a consonant-glide-vowel (CgV) string. On the other hand, camxes allows cmavo to include it:
cmavo-form <- !h !cluster onset (nucleus h)* (!stressed nucleus / nucleus !cluster) / y+ / digit
onset <- h / consonant? glide / initial[Version 119 of PEG morphology page.]
The BPFK disallows CgV in cmevla/fu'ivla/ma'ovla.
It is a stronger restriction than that of CLL, which allows CgV at least in cmevla and fu'ivla. We need therefore to take measures to rescue the existing words that become invalid under the new rule.
CgV words on la jbovlaste will be moved into obsolete words category. In order to rescue the words, the following measures can be taken:
- add an apostrophe between Cg and V, and then "CgV" will be separated into two syllables "CV,V"; ex.) kuarka -> ku'arka;
- Attention 1: if the method transforms the word into (pseudo-)lujvo ("fiakre", "fiesta", "kuardicka'u", "tiatro"), it cannot be applied;
- Attention 2: if the method transforms the word into a bad fu'ivla that fails in slinku'i ("ckankua": it is currently (2015-01-04) downvoted, but can revive someday), it cannot be applied;
- or make the glide letter double, and then "CgV" will be separated into two syllables "CV,gV"; ex.) ckankua -> ckankuua;
- Attention: for fu'ivla beginning with CgV and/or (C)V(g)CCgV..., this method cannot be applied because camxes will regard the result as two words; ex.) fiakre -> fi + iakre; madjio -> ma + djiio;
- if neither 1 nor 2 can be applied,
- turn it back into type-3 fu'ivla; ex.) fiakre -> marcrfi'akre/marcrfiiakre;
- create a corresponding lujvo; ex.) kuardicka'u -> ratslepaudicka'u;
- turn it back into a zi'evla using a hyphen "n"; ex.) kuardicka'u -> ku'andicka'u;
- reformulate it into zei-lujvo; ex.) kuardicka'u -> ku'arka zei dicka'u;
- create another fu'ivla; ex.) kuardicka'u -> ku'arkadicka'u.