Mat 17:9 Tell the vision to no man, until the Son of man be risen again from the dead.

Christ uses sight as a symbol for the physical, but there is always a sense that the physical is an temporary illusion, an effect of the deeper reality of the spirit. The use of "vision" here carries both the sense that the transfiguration was both real and an illusion which is consistent with the Greek. The insertion of the word "again" in the English indicates that Christ's resurrection is a repeat of this event, but in the original Greek, there is no word indicating "again." It is a complete invention of the translators to make a point.

A more literal translation: Tell noone about this vision until the Son of man is raised from a corpse.

"Vision" is from the Greek horama, which means "a sight," "a visible object," "a spectacle," "a vision," and "a dream."

"Rise up" is from anistêmi, which is a version of histêmi, from the last verse, which means "to make a stand," "to set up," "to place," or "to stand." The prefix "ana" is added which means "into the midst" and "among." This gives it the meaning of "to rouse from sleep," "to raise from the dead," "to make ascend," and "to rise up and go away."

"Dead" is from nekros, which specifically means "a corpse" as well as "the dead." This is different from the word used just a few verses ago to describe the apostles death. That "death" was thanatos, which means "death" and "a death sentence."