a person who thanks or expresses gratitude

[kadioguy]

thanker
noun
a person who thanks or expresses gratitude

https://www.collinsdictionary.com/dictionary/english/thanker
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Why not a person who thanks to somebody or expresses gratitude?

'thank' is a transitive verb, isn't it?

 

[Rover_KE]

Yes. That's why 'to' after 'somebody' is wrong.

The dictionary example could have been 'a person who thanks somebody ...' but you should know by now that dictionary editors don't include unnecessary words.

 

[kadioguy]

Yes. That's why 'to' after 'somebody' is wrong.

Sorry, I should have said 'Why not a person who thanks somebody ...'.
But did you mean That's why 'to' before 'somebody' is wrong?

 

[Rover_KE]

Sorry, I should have said 'Why not a person who thanks somebody ...'.

But did you mean That's why 'to' before 'somebody' is wrong?

Yes. Sorry about that.