silver wedding anniversary
noun [ C usually singular ] uk/ˌsɪl.və ˈwed.ɪŋ / us/ˌsɪl.vɚ ˈwed.ɪŋ / (US also silver anniversary); (UK also silver wedding)
结婚25周年纪念日，银婚
the date exactly 25 years after the date of a marriage
See also: golden wedding anniversary