Salaamun Alaykum.
We use to say 'Zazak Allahh Khair' to 'thank someone' or sometimes 'wish something better for that person' in return, like we say 'thanks' or 'thank you' or 'wish you...' in English.
Would like to share my understand here regarding 'Zazak Allahh Khair'.
From yt142 we understand that Al-Zaza' means 'the recompense' (explanation of aya 76:22) and from yt64 (timestamp 9.50 onward) 'Khair' means 'proper application/ understanding of the scripture' (aya 2:61). Dr. Hany made it clear that 'Khair' doesn't mean 'general good'.
So far what I understand that 'Zazak Allahh Khair' means Allahh SWT 'recompenses' for 'proper application/ understanding of the scripture'. There is no 'thanking' or 'wishing for someone else' here!
Would like to hear from other toilers on this...
Baraka Gerngross
Recompense is used as a synonym of reward. But as noun and verb they indicate more meaningful ways of usages.
As noun recompense means to compensate for an injury while reward is something of value given in return for an act.
As verb recompense means to reward or repay (someone) for something done, given etc.; while reward is (obsolete|transitive) to give (something) as a reward.
I find it 'Jazakum Allah Khairan' in common Arabic, which usually means 'May (what's the proper Arabic word here?) Allah reward (not recompense) you with better'.
Is there any difference in Arabic grammar usages?
Amine Yeager
It means "may Allah reward you with better understanding".
I would just stick to salamun alaikum tho
Asma Nooruddin
Reading the post, I also thought that may Allah compensate you with better understanding of the Scripture. Which we all need in the self-correcting methodological path, don't we?