termifra lujvo

x1 is a code system by which x2 is encoded into x3.

See also te, mifra, selmifra.

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.
selmifra
x1 is plain text encoded into x2 through code system x3.