καὶ ἐν τούτῳ γινώσκομεν ὅτι ἐγνώκαμεν αὐτόν, ἐὰν τὰς ἐντολὰς αὐτοῦ τηρῶμεν.

1. καὶ
   and
2. ἐν
   in
3. τούτῳ
   this
4. γινώσκομεν
   we know
5. ὅτι
   that
   because
6. ἐγνώκαμεν
   we have known
   have known
7. αὐτόν
   him
8.  
   ,
    
9. ἐὰν
   if
10. τὰς
    the
11. ἐντολὰς
    commandments
12. αὐτοῦ
    his
13. τηρῶμεν
    we keep
14.  
    .
     

And by this we know that we have known him, if we keep his commandments.