How to say "head" and "tails" when flipping a coin?
Chinese use 正反 more than US people use obverse/reverse.

Other words are  花/字, but the side is controversial.

The side of 中华人民共和国 is 正面, but many many people think 1元 is 正面, this would be more confused if you use 字/花. Which side is 字, is it 正面?


China bank realized this problem, the new coin:



Now 中国人民银行and 1 元 are on the same side, that is 正面, in this case 字 is 正面, 花 is 反面.

In some dialect, people use 字/背.