ὅτι αὕτη ἐστὶν ἡ ἀγγελία ἣν ἠκούσατε ἀπ᾽ ἀρχῆς, ἵνα ἀγαπῶμεν ἀλλήλους,

1. ὅτι
   that
   because
2. αὕτη
   this
3. ἐστὶν
   is
4. ἡ
   the
   or
5. ἀγγελία
   message
   news
6. ἣν
   was
7. ἠκούσατε
   you heard
8. ἀπ᾽
   from
9. ἀρχῆς
   beginning
10.  
    ,
     
11. ἵνα
    so that
12. ἀγαπῶμεν
    we love
    we should love
13. ἀλλήλους
    one another
14.  
    ,
     

That this is the message which you heard from the beginning, so that we should love one another.