Origin: Greek suffix -osis
Hypnosis has 2 different meanings across 1 category:
a state that resembles sleep but that is induced by suggestion
"The performer guided the audience into hypnosis, creating a state that resembled sleep but was actually induced by powerful suggestion."
A trancelike state, artificially induced, in which a person has a heightened suggestibility, and in which suppressed memories may be experienced.
"The therapist used hypnosis to help the patient recall repressed childhood trauma while she remained in a deeply relaxed, trance-like condition."
In plain English: Hypnosis is a state where you are so focused that it feels like you can't control your own thoughts or actions.
"The stage hypnotist put several volunteers into hypnosis to perform silly tricks on audience members."
Usage: Do not confuse the noun "hypnosis" with the verb "to hypnotize," as they refer to distinct grammatical forms of the same concept. This term is often misused when people describe the act itself rather than the state, so ensure you use it only for the condition or session, not the process of inducing it.
From modern scholarly Ancient Greek ὕπνωσις (húpnōsis), which formation closes the derivational gap between the ancient words ὑπνόω (hupnóō, "I put to sleep") and ὑπνωτικός (hupnōtikós, "sleep-inducing, soporific"). Ultimately traces back to ὕπνος (húpnos, "sleep").