1624. What character can be added to both of these characters to give other characters? 馬_ -> _殳

Answer:

馬  BA, uma, ma  - horse

殳  ZU, SHU, mata, hoko - pole, beat with a stick 

Add 区:馬+区 区+殳 

区  KU - district

駆  KU, kake(ru), ka(ru) - gallop, run, rush, drive, spur on

殴  OU, nagu(ru) - beat, strike