Second-person singular present simple form of believe(verb)
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Use "believest" in a sentence
"Thus the heavens and the earth were finished, and all in five days, and all less than six thousand years ago; and if thou believest it not, in a sling shalt thou find thy hindermost quarters"
"Truly i believest that i was posting a comment aligned to thy previous post concerning the iRANT Keyboard."
"“Wretched man! believest thou not that after death comes the judgment?”"