The twilight language (Sanskrit:sandha-bhasa, Tibetan:gongpe-ke) is a polysemic language and communication system associated with tantric traditions in Vajrayana Buddhism and Hinduism. It includes visual communication, verbal communication and nonverbal communication. Tantric texts are often written in a form of the twilight language that is incomprehensible to the uninitiated reader. As part of an esoteric tradition of initiation, the texts are not to be employed by those without an experienced guide and the use of the twilight language ensures that the uninitiated do not easily gain access to the knowledge contained in these works. According to Judith Simmer-Brown:
As has often been said, tantric texts are written in "twilight language" (sandha-bhasa, gongpe-ke), which, as the Hevajra-tantra states, is a "secret language, that great convention of the yoginis, which the shravakas and others cannot unriddle". This means that the texts of Buddhist tantra cannot be understood without the specific oral commentary by authorized Vajrayana teachers.