lerfu -ler-le'u- gismu

x1 (la'e zo BY/word-bu) is a letter/digit/symbol in alphabet/character-set x2 representing x3.

Also x1 glyph, rune, character (also me'o BY/word-bu), x2 symbol set; (adjective:) x1 is alphabetic/symbolic; "letteral" used by analogy with "numeral"; sinxa is the more generic symbol. See also mifra, namcu, sinxa, pandi.

In definition:

foi
terminator: end composite lerfu; never elidable.
xo
digit/number: number/digit/lerfu question.
joi'i (exp!)
mekso string operator (n-ary): formal right-concatenation; X1 + X, where Xi is a string/word/text/character/letteral/lerfu/quoted utterance (quote appropriately iff necessary; preserve and be careful about the use-vs.-mention distinction) for all i.
burfava
x1 is a part of Lojban text representing rule 'lerfu-word' according to the first edition of the book 'The Complete Lojban Language'.
lerfusu
x1 is a part of Lojban text representing rule 'lerfu-string' according to the first edition of the book 'The Complete Lojban Language'.

In notes:

mifra
x1 is encoded/cipher text of plain-text x2 by code/coding system x3; x1 is in code; x3 is a code.
namcu
x1 (li) is a number/quantifier/digit/value/figure (noun); refers to the value and not the symbol.
pandi
x1 (agent) punctuates x2 (expression) with symbol/word x3 with syntactic/semantic effect x4.
sinxa
x1 is a sign/symbol/signal representing/referring/signifying/meaning x2 to observer x3.
bu'ivla
x1 (quoted text) is a “bu letteral” of character x2 (zoi quote).
jbole'u
le1=lo1 (la'e zo BY/word-bu) is a letter/digit/symbol of Lojban’s alphabet representing le3
jifpedle'u
x1 is a "false friend" (letter/symbol in a different writing system that looks similar, but differs significantly in meaning) to x2, in alphabet/character-set x3 representing x4
lerci'e
x1=c1 is a script/writing system with rules x2=c2 among glyphs x3=c3=l1 displaying x4=c4
lerpavmoivla
l1 (quoted letteral) is the first letter of the word v1.
lertermifra
m3 is a character encoding for bytes m2 with symbols/font m1.
lervla
v1 is a word which stands for the letter/digit/symbol v2=l1 in language v3.
leryrolmoivla
l1 (quoted letteral) is the last letter of the word v1.
ornyle'u
x1 is a digraph in alphabet/character-set x2 representing x3 in language x4
padle'u
x1 is punctuation in orthography/language x2 representing x3
vlalerpoici'e
x1 is a script/orthography for language x2
xanle'ule'u
xl1 (la'e zo BY/word-bu) is a fingerspelling sign in character-set of sign language/system of manual communication xl2 representing letter/digit/symbol xl3=l1 in written alphabet/character-set xl2 performed by hand(s) xl4.
zilterle'u
x1=l2 is a formal character-set/alphabet containing letter(s)/characters/digits/terms x2=l1; x2 is a letter in formal alphabet x1 and is treated formally (it has no meaning, other than possibly being distinct from other letters in x1)
glife
x1 is a glyph, elemental symbol within an agreed set of symbols, intended to represent character x2
bei'a
quotes a non-Lojban letter
bei'au
quotes non-Lojban letters (delimited)
ge'ai (exp!)
metasyntactic variable prenex
ge'ei (exp!)
metasyntactic variable marker
moi'u (exp!)
x1 is (n)th member of alphabet/set x2 ordered by rule x3, where the count begins at x4.
abjadu
x1 is an abjad used to write x2.
anji
x1 is a sinogram / Chinese hanzi / Japanese kanji (logogram) with meaning x2 and radical x3.
ga'elfu
x1 (la'e zo BY/word-bu) is a capital/capitalised/upper-shift letter/digit/symbol in alphabet/character-set x2 representing x3.
jbopomofo
x1 is a jbopomofo orthography (bopomofo orthography adapted for lojban)
katkana
x1 is a katakana (Japanese syllabary) of sound x2.
lu'erma
x1 (letteral) is a letter that occurs in word x2 (text); x2 contains an occurrence of x1 as a digit/term in a sequence
namsusu
x1 is a part of Lojban text representing rule 'number' according to the first edition of the book 'The Complete Lojban Language'.
slurume
x1 is a part of Lojban text representing rule 'free' according to the first edition of the book 'The Complete Lojban Language'.
to'alfu
x1 (la'e zo BY/word-bu) is a lower-case letter/digit/symbol in alphabet/character-set x2 representing x3.
vlaleci'e
x1 is a script/orthography for language x2
xangulu
x1 is a hangul (Korean alphabet) of sound x2.
xirgana
x1 is a hiragana (Japanese syllabary) of sound x2.
ce'a zei ciste
x1 (mass) is a font interrelated by rules or relations x2 among components x3 (full set) displaying x4 (property of x1).
ci zei mektika
x1 is a part of Lojban text representing rule 'operand-3' according to the first edition of the book 'The Complete Lojban Language'.
ga'e zei lerfu
x1 (la'e zo BY/word-bu) is a capital/capitalised/upper-shift letter/digit/symbol in alphabet/character-set x2 representing x3.
re zei taulka
x1 is a part of Lojban text representing rule 'tanru-unit-2' according to the first edition of the book 'The Complete Lojban Language'.
to'a zei lerfu
x1 (la'e zo BY/word-bu) is a lower-case letter/digit/symbol in alphabet/character-set x2 representing x3.
xa zei sumtika
x1 is a part of Lojban text representing rule 'sumti-6' according to the first edition of the book 'The Complete Lojban Language'.