What is the difference between 妥善 and 妥当? As with the case on many words in Mandarin, 妥善 and 妥当 both mean "appropriate" or "proper" in English. 

However, what is the difference between these two words, and how can I use it properly?
Both '妥善' and '妥当' means  "appropriate" or "proper" . 

There are minor difference: 

'妥善' implies  "(satisfactorily) appropriate"

'妥当' implies "(correctly) appropriate"

Example:


對員工遣散有妥善安排 = There is a proper arrangement for severance. (everyone should be satisfied)
對員工遣散有妥当安排 = There is a proper arrangement for severance. (everything by the book without mistake)
妥善地佈防 = properly set up defensive positions (satisfactory on all accounts)
妥当地佈防 = properly set up defensive positions (follow all protocols correctly)


If someone said he will give you a 妥善的補償, he is trying to assure you that the compensation will be fair and satisfactory; If he said he will give you a 妥当的補償, it means you will get whatever you are entitled to. No more, no less.