before vowels somn-, word-forming element meaning "sleep," from combining form of Latin somnus "sleep, slumber," from PIE root *swep- "to sleep."
Entries linking to somni-
*swep-
Proto-Indo-European root meaning "to sleep."
It forms all or part of: hypno-; hypnosis; hypnotic; hypnotism; insomnia; somni-; somnambulate; somniloquy; somnolence; somnolent; Somnus; sopor; soporific.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit svapnah, Avestan kvafna-, Greek hypnos, Latin somnus, Lithuanian sapnas, Old Church Slavonic sunu, Old Irish suan, Welsh hun "sleep;" Latin sopor "a deep sleep;" Old English swefn, Old Norse svefn "a dream."
somnial adj.
"pertaining to or involving sleep," 1690s; see somni- + -al (1).