The most common way to say good night in Russian is спокойной ночи (spakóynay nóchi). Which is a contraction of the phrase Желаю тебе спокойной ночи (I wish you a quiet night).
Спокойной is a form of спокойный, which means ‘calm, gentle, pacific, secure, sober, collected, cool, level, quiet, settled, tranquil, cosh, comfortable, immovable, peaceful, sedate, steady, reposeful, cool-headed, orderly, restful, smooth, unruffled, sober-blooded, composed, imperturbable, placid, serene, still, douce’.
Related expressions include:
– спокойная жизнь = a restful life
– спокойная вода = calm water
– спокойное море = serene
– спокойные цвета = quiet colours
– спокойный нрав = even temper
– спокойствие духа = peace of mind
Ночи is a form of ночь, which means night.
Related expressions include:
– ночной столик = bed-side table
– ночной сторож = watchman
– ночной цветок = night-flower
Other ways to wish someone a good night in Russian include:
– Доброй ночи = Good night
– Сладких снов = Sweet dreams
– Приятных снов = Pleasant dreams
Сладких is a form of сладкий, which means ‘honeyed, sweet, luscious, mellow’.
Снов is a form of сон, which means ‘sleep, dream, slumber, rest, repose, shut-eye’.
Приятных is a form of приятный, which means ‘acceptable, sweet-tempered, goodly, likable, palatable, soft, kindly, good, grateful, lovesome, pleasing, satisfactory’.
Are there other ways to wish someone a good night in Russian?
There are two errors in your Russian: first, it’s “спокойной ночи”, as in the full form; second, the conjunction here should be “и” (non-contrasting), not “а” (contrasting).
“Доброй ночи” is also acceptable at going to sleep, but it’s more common as a form of late evening meeting/parting utterance.
Very informally, “сладких снов” can be shortened to simply “снов”.
These phrases often depend on whom one is talking. If one wishes it to a small child, it’s either standard “спокойной ночи” or “баю-бай” or “баюшки-баю” (rock-a-bye) or a combination of all the above, followed by “Пусть тебе приснится [something please to see in a dream]” and/or a lullaby (later, after two hours of failed attempts to get a child to sleep, the phrase might sound like “Давай спи уже”, which is a very informal way of saying “Sleep already!” but it’s not very efficient).
My favourite (also very informal) way of saying good night is “Отбой” (bed time, lights off). But the latter is also usually followed by “Спокойной ночи” and “Приятных снов”.