china wedding anniversary; 20th wedding anniversary
Refers specifically to the 20th wedding anniversary, traditionally associated with china (porcelain).
My parents will celebrate their china wedding anniversary this year.
To celebrate their 20th wedding anniversary, the couple took a pottery class together.
Refers to the 50th wedding anniversary (golden wedding), while 磁器婚式 is the 20th.
Refers to the 25th wedding anniversary (silver wedding), while 磁器婚式 is the 20th.
Compound of 磁器 (じき, 'porcelain, china') and 婚式 (こんしき, 'wedding ceremony'), following the Western tradition of naming wedding anniversaries after materials.