Lojban pronunciations are defined using the International Phonetic Alphabet, or IPA, a standard method of transcribing pronunciations. By convention, IPA transcriptions are always within square brackets: for example, the word “cat” is pronounced (in General American pronunciation) [kæt]. Section 3.10 contains a brief explanation of the IPA characters used in this chapter, with their nearest analogues in English, and will be especially useful to those not familiar with the technical terms used in describing speech sounds.

The standard pronunciations and permitted variants of the Lojban letters are listed in the table below. The descriptions have deliberately been made a bit ambiguous to cover variations in pronunciation by speakers of different native languages and dialects. In all cases except r the first IPA symbol shown represents the preferred pronunciation; for r , all of the variations (and any other rhotic sound) are equally acceptable.

The Lojban sounds must be clearly pronounced so that they are not mistaken for each other. Voicing and placement of the tongue are the key factors in correct pronunciation, but other subtle differences will develop between consonants in a Lojban-speaking community. At this point these are the only mandatory rules on the range of sounds.

Note in particular that Lojban vowels can be pronounced with either rounded or unrounded lips; typically o and u are rounded and the others are not, as in English, but this is not a requirement; some people round y as well. Lojban consonants can be aspirated or unaspirated. Palatalizing of consonants, as found in Russian and other languages, is not generally acceptable in pronunciation, though a following i may cause it.

The sounds represented by the letters c , g , j , s , and x require special attention for speakers of English, either because they are ambiguous in the orthography of English ( c , g , s), or because they are strikingly different in Lojban ( c , j , x). The English “c” represents three different sounds, [k] in “cat” and [s] in “cent” , as well as the [ʃ] of “ocean”. Similarly, English “g” can represent [ɡ] as in “go” , [dʒ] as in “gentle” , and [ʒ] as in the second "g" in “garage” (in some pronunciations). English “s” can be either [s] as in “cats” , [z] as in “cards” , [ʃ] as in “tension” , or [ʒ] as in “measure”. The sound of Lojban x doesn't appear in most English dialects at all.

There are two common English sounds that are found in Lojban but are not Lojban consonants: the “ch” of “church” and the “j” of “judge”. In Lojban, these are considered two consonant sounds spoken together without an intervening vowel sound, and so are represented in Lojban by the two separate consonants: tc (IPA [tʃ]) and dj (IPA [dʒ]). In general, whether a complex sound is considered one sound or two depends on the language: Russian views “ts” as a single sound, whereas English, French, and Lojban consider it to be a consonant cluster.