From the Lojban web site FAQ (http://www.lojban.org/files/brochures/faq.htm):
rafsi: building block(s) of lujvo compound words
An affix — with the proviso that all gismu have one or more of them. Affixes are rather more plentiful in Lojban than they tend to be in most languages.
Quick summary:
- 1342 (all) gismu have 5-letter rafsi (itself)
- 1337 (all but brodV) gismu have 4-letter rafsi (itself sans final vowel)
- 1103 gismu have at least one 3-letter rafsi
- 207 gismu have 3-letter rafsi of the form CCV
- 833 gismu have 3-letter rafsi of the form CVC
- 393 gismu have 3-letter rafsi of the form CVV
- 5 gismu (bloti cmene cmoni rotsu zgike) have both CCV and CVV
- 48 gismu have both CVC and CCV
- 238 gismu have both CVC and CVV
- 2 gismu (bloti rotsu) have all three
- what about 'condi'? --pne
- 94 cmavo have at least one 3-letter rafsi
- 2 cmavo (da je) have 3-letter rafsi of the form CCV
- 83 cmavo have 3-letter rafsi of the form CVC
- 28 cmavo have 3-letter rafsi of the form CVV
- 2 cmavo (da je) have both CCV and CVC
- 12 cmavo have both CVC and CVV
They top ten most frequently used rafsi on IRC are sel, jbo, pre, tol, sam, smu, sku, bau, nor, and vla. For a complete list, see the attached file.
See also Desirability of rafsi