The pronoun marking a class, as being of those who know not.
What shall be on the morrow (τὸ τῆς αὔριον)
Lit., the thing of the morrow. The texts vary. Westcott and Hort read, Ye know not what your life shall be on the morrow, for ye are a vapor: thus throwing out the question.
What is your life? (ποία)
Lit., of what kind or nature.
It is even a vapor (ἀτμὶς γάρ ἐστιν)
But all the best texts read ἐστε, ye are. So Rev., which, however, retains the question, what is your life ?
Appeareth - vanisheth
Both participles, appearing, vanishing.
And then (ἔπειτα καὶ)
The καὶ placed after the adverb then is not copulative, but expresses that the vapor vanishes even as it appeared.