Planao (πλανάω) means to lead astray, to cause to wander, to deceive. It derives from the root plane (wandering), from which we also get the English word "planet" (a wandering star). In the active voice it means to cause someone to go astray or to mislead; in the passive it means to be led astray, to wander, or to be deceived. The word carries the sense of being diverted from the true path — whether doctrinally, morally, or spiritually.
Jesus repeatedly warned against deception as a hallmark of the last days: "See that no one leads you astray" (Matthew 24:4). The word planao appears frequently in the Olivet Discourse and in the epistles as a warning against false prophets, false Christs, and false teachers who would deceive even the elect if possible (Matthew 24:24). In 1 John 2:26, John warns about those attempting to planao (deceive) believers. The passive form emphasizes personal responsibility — one can be "wandering" through negligence or willful departure from truth. James 5:19 speaks of recovering one who has "wandered from the truth." The theological weight of this word underscores the necessity of sound doctrine, vigilance, and anchoring oneself in Scripture to avoid spiritual deception.