2208 רָצַח (rāṣaḥ) murder, slay, kill.
Derivative 2208a רֶצַח (reṣaḥ) shattering (Ps 42:11;, Ezk 21:27).

rāṣaḥ is a purely Hebrew term. It has no clear cognate in any of the contemporary tongues. The root occurs thirty-eight times in the ot, with fourteen occurrences in Num 35. The initial use of the root appears in the Ten Commandments (Ex 20:13). In that important text it appears in the simple Qal stem with the negative adverb, “You shall not murder,” being a more precise reading than the too-general KJV “thou shalt not kill.” Much has been made of the fact that the root rāṣaḥ appears in the Mosaic legislation, as though this term bore a special connotation of premeditation, as though the Decalogue only proscribed premeditated crime. This is not the case. The many occurrences in Num 35 deal with the organization of the six cities of refuge to which manslayers who killed a person accidentally could flee. Numbers 35:11 makes completely clear that the refuge was for those guilty of unpremeditated, accidental killings. This makes clear that rāṣaḥ applies equally to both cases of premeditated murder and killings as a result of any other circumstances, what English Common Law has called, “man slaughter.” The root also describes killing for revenge (Num 35:27, 30) and assassination (II Kgs 6:32). It appears in a few poetic contexts, as an “A” word in a peculiar parallel construction (Job 24:14); as an “A” word parallel to a general term for immorality, zimmâ (Hos 6:9); as a “B” word parallel to another synonym “to kill,” “to slay” (Ps 94:6). In only one case in the whole ot is the root used of the killing of man by an animal (Prov 22:13). But even in that context it is the enormity and horror of the deed which is primary. In all other cases of the use of rāṣaḥ, it is man’s crime against man and God’s censure of it which is uppermost.

Harris, R. L., Harris, R. L., Archer, G. L., & Waltke, B. K. 1999, c1980. Theological Wordbook of the Old Testament (electronic ed.) . Moody Press: Chicago