retainer (suomeksi)

ennakkopalkkio (s: a fee charged for services)
ennakkomaksu (s: a fee charged for services)
varausmaksu (s)
pidike (s: any thing or person that retains)
pidätin (s)
kiinnitin (s: any thing or person that retains)
palvelija (s: a paid servant, especially one who has been employed for many years)
hammastuki (s: a device that holds teeth in position after orthodontic treatment)