lu'erfu
fu'ivla x_{1} (quote) is a text/word/sequence wherein the characters/phonemes are taken over alphabet x_{2} (set) For formal language analysis. In mathematical writing, this relationship is sometimes written as "/"; the set of all x1 (where x2 is specified) is x2* (where "*" is the Kleene star); then x1 is an element/member of x2*, and the letters of x1 are elements/members of x2. While each letter in x1 must be an element of x2, there can be elements of x2 that do not appear in x1.


lu'erma
fu'ivla x_{1} (letteral) is a letter that occurs in word x_{2} (text); x2 contains an occurrence of x1 as a digit/term in a sequence See also: lu'erfu (for words over an alphabet), lerfu (for letters/digits/terms/elements/members of an alphabet; for completely formal usage (without any meaning), use: se zilterle'u)


zilterle'u
lujvo x_{1}=l_{2} is a formal characterset/alphabet containing letter(s)/characters/digits/terms x_{2}=l_{1}; x_{2} is a letter in formal alphabet x_{1} and is treated formally (it has no meaning, other than possibly being distinct from other letters in x_{1}) Used for formal language analysis. See also: lu'erma, lu'erfu, lerfu (for a nonformal, potentially meaningful variant  with reordered terbri)
