1. alethes = true (*1) (as contrasted with what is false).  Hence, used of God (John 3:33) in that He cannot lie (see also John 5:31;  8:13).  The opposite of a lie.  Gr. apseudes.  Tit. 1:2.  Cp. John 4:18.
1John 2:27.

2 alethinos = very (*1).  Fr. veritable:  i.e. genuine, real, substantial, as contrasted with that which is fictitious, unreal, shadowy, or symbolical.  Hence, alethinos is that which has truth for its base and is all that it claims to be (John 6:32;  15:1).  See 1Thess. 1:9.  Heb. 8:2;  9:24.

3. gnesios = legitimate.  Spoken of children.  Occ. only in Phil. 4:3.  1Tim. 1:2  Tit. 1:4.  With Art. = sincerity (2Cor. 8:8).  The Adverb gnesios = naturally, occ. only in Phil. 2:20.

4. pistos = faithful.  A verbal Adj., from peitho = to persuade, and Pass. to be persuaded and convinced.  Hence, believing, faithful, trustworthy.  Transl. "true" in 2Cor. 1:18.  1Tim. 3:1  See Ap. 150. III.