ei (Greek #1487)
if, whether, that, etc.
KJV usage: forasmuch as, if, that, (al-)though, whether. Often used in connection or composition with other particles, especially as in 1489, 1490, 1499, 1508, 1509, 1512, 1513, 1536, 1537. See also 1437.
Pronounce: i
Origin: a primary particle of conditionality
esti (Greek #2076)
he (she or it) is; also (with neuter plural) they are
KJV usage: are, be(-long), call, X can(-not), come, consisteth, X dure for a while, + follow, X have, (that) is (to say), make, meaneth, X must needs, + profit, + remaineth, + wrestle.
Pronounce: es-tee'
Origin: third person singular present indicative of 1510