ἐὰν εἴπωμεν ὅτι κοινωνίαν ἔχομεν μετ᾽ αὐτοῦ καὶ ἐν τῷ σκότει περιπατῶμεν, ψευδόμεθα καὶ οὐ ποιοῦμεν τὴν ἀλήθειαν·

1. ἐὰν
   if
2. εἴπωμεν
   let us say
   we say, let us speak
3. ὅτι
   that
   because
4. κοινωνίαν
   relationship
   partnership
5. ἔχομεν
   we have
6. μετ᾽
   with
7. αὐτοῦ
   his
8. καὶ
   and
9. ἐν
   in
10. τῷ
    the
    to the
11. σκότει
    darkness
12. περιπατῶμεν
    we walk
13.  
    ,
     
14. ψευδόμεθα
    we lie
15. καὶ
    and
16. οὐ
    not
17. ποιοῦμεν
    we do
    we make
18. τὴν
    the
19. ἀλήθειαν
    truth
20.  
    ·
     

If we say that we have relationship with him and walk in the darkness, we lie and do not practice the truth.