Οὗτός ἐστιν ὁ μαθητὴς ὁ μαρτυρῶν περὶ τούτων καὶ γράψας ταῦτα, καὶ οἴδαμεν ὅτι ἀληθής ἐστιν ἡ μαρτυρία αὐτοῦ.

1. Οὗτός
   This
2. ἐστιν
   is
3. ὁ
   the
4. μαθητὴς
   disciple
5. ὁ
   the
6. μαρτυρῶν
   witnesses
   of witnesses, testifying
7. περὶ
   about
   concerning
8. τούτων
   of these
   these
9. καὶ
   and
10. γράψας
    having written
11. ταῦτα
    these
    these things
12.  
    ,
     
13. καὶ
    and
14. οἴδαμεν
    we know
15. ὅτι
    that
    because
16. ἀληθής
    true
17. ἐστιν
    is
18. ἡ
    the
    or
19. μαρτυρία
    testimonies
    testimony
20. αὐτοῦ
    his
21.  
    .
     

This is the disciple who testifies concerning these things and has written these things, and we know that his testimony is true.