Harmless - Vine's Expository Dictionary of New Testament Words
Harmless[ 1,,G185, akeraios ]
lit., unmixed, with absence of foreign mixture" (from a, negative, and kerannumi, "to mix"), "pure," is used metaphorically in the NT of what is guileless, sincere, Matthew 10:16, "harmless" (marg., "simple"), i.e., with the simplicity of a single eye, discerning what is evil, and choosing only what glorifies God; Romans 16:19, "simple (unto that which is evil)," AV marg., "harmless;" Philippians 2:15, "harmless," AV marg., "sincere." The Greeks used it of wine unmixed with water, of unalloyed metal; in the papyri writings it is used of a loan the interest of which is guaranteed (Moulton and Milligan, Vocab.). Trench compares it and synonymous words as follows: "as the akakos (See No. 2, below) has no harmfulness in him, and the adolos no guile, so the akeraios no foreign mixture, and the haplous no folds" (Syn. lvi). Haplous is said of the single eye, Matthew 6:22; Luke 11:34.
[ 2,,G172, akakos ]
the negative of kakos (See HARM, A, No. 1), "void of evil," is rendered "harmless" in Hebrews 7:26 (RV, "guileless"), of the character of Christ as a High Priest; in Romans 16:18, RV, "innocent," AV, "simple."