Simple in NT

Roman 16:18-19
18 For they that are such serve not our Lord Jesus Christ, but their own belly; and by good 
words and fairspeeches deceive the hearts of the simple. 19 For your obedience is come 
abroad unto all men. I am glad therefore on your behalf: but yet I would have you wise 
unto that which is good, and simple concerning evil.


akakos
a[kakoß - Strongs #172 from ( #1 a and kakos #2556)
Thayer and Smith's Bible Dictionary
without guile or fraud, harmless, free from guilt fearing no evil from others, distrusting no one
King James New Testament - used 2 x Romans (simple Romans 1:18) Hebrews(harmless)

Romans 16:18 For they that are such serve not our Lord Jesus Christ, but their own belly; and by good words and fairspeeches deceive the hearts of the simple. 

Hebrews 7:26 For such an high priest became us, who is holy, harmless, undefiled, separate from sinners, and made higher than the heavens; 

akeiraios
ajkevraioß - Strongs #185
Thayer and Smith's Bible Dictionary
unmixed, pure as in wines or metals
of the mind, without a mixture of evil, free from guile, innocent, simple
King James New Testament - used 3 times
harmless 2(Matthew 10:16, Philippians 2:15), simple 1(Romans 16:19)

Matthew 10:16 Behold, I send you forth as sheep in the midst of wolves: be ye therefore wise as serpents, and harmless as doves. 

Romans 16:19 For your obedience is come abroad unto all men. I am glad therefore on your behalf: but yet I would have you wise unto that which is good , and simple concerning evil. 

Philippians 2:15 That ye may be blameless and harmless, the sons of God, without rebuke, in the midst of a crooked and perverse nation, among whom ye shine as lights in the world; 

* Note Simplicity is found in the KJV in the New Testament
 ἁπλότης 'haplotes' (Strong's #572) is used 8 times in the church epistles: Rms 12:8; II Cor 1:12; 8:2; 9:11,13; 11:3; Eph 6:5, Col 3:22.
KJV (8) - bountifulness, 1; liberality, 1; liberty, 1; simplicity, 3; singleness, 2;