Third-person singular simple present indicative form of sin.(verb)
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Use "sinneth" in a sentence
"From the devil there is not generation, but corruption [Bengel]. sinneth from the beginning -- from the time that any began to sin"
"8 He that committeth sin is of the devil; for the devil sinneth from the beginning."
"Since the fall of man [at the beginning of our world] the devil is (ever) sinning (this is the force of "sinneth"; he has sinned from the beginning, is the cause of all sins, and still goes on sinning; present)."