Digit/number: pi (denoted "π"; approximately 3.1416...); the constant defined by the ratio of the circumference to the diameter of all circles in Euclidean space.

This word is intended to be an alternative to but synonymous with both "pai" as defined in the original Lojban baseline grammar, as well as the related proposed meaning of "pi'au". Consequent to the latter, it is part of a proposal to move "pau" to "pai" and "poi'a", "noi'a", "soi'a" to "pau", "nau", and "sau" resp. See also: "tau'u". For reference: "tcekitau", "2 to communicate x_{3} (si'o/du'u)">tcekitaujau", "tcekitaujei";
https://mw.lojban.org/papri/ce_ki_tau_jau .

- tau'u
*(exp!)* - digit/number: tau (denoted "τ": approximately 6.2831...). The constant defined by the ratio of the circumference to the radius of all circles (default: in Euclidean geometry).