Space flight involves a lot of technical terms and acronyms. This glossary gives an expansion or brief description of many of those most likely to occur. (Currently very limited and only in Russian; we'd appreciate any help in improving both our coverage and in providing English explanations!)

Yuri Gagarin's callsign
Lilies of the Valley
A popular song of the time, which the cosmonauts had adopted as a private joke.
The cosmonauts jokingly called each other 'Lilies of the Valley', having parodied the love song, turning it into a drinking song.
Callsign for HF radio stations
Vesna (“spring”) was used as callsigns of radio stations in Moscow and Khabarovsk, operating on HF rather than VHF.
One of the mission communication systems, and callsigns for the ground stations
Zaria (“dawn”) was both the name of one of the mission communications systems, and used as callsigns for the ground stations. The Zaria communications system was designed by NII-695, led by their Chief Designer Yuriy Sergeyevich Bykov, who was present at the Zaria-1 ground station at the launch site.
динамический электромагнитный микрофон шлема
прибор контроля режима спуска
Shutter mode control unit
тормозная двигательная установка
The spacecraft's retropopulsion system.