συνοιδα is closely related to συνειδω. In “The Complete Word Study Dictionary New Testament” they are even listed under the same number: G4894. Like οἰδα it means to be aware or conscious of something. This is a deeper awareness, though. συνειδω is often associated with self-consciousness or self-awareness. συνοιδα is only used twice in the New Testament (Acts 5:2; 1Cor. 4:4); it is also used twice in the Greek translation of the Old Testament (Lev 5:1; Job 27:6).
and kept back some of the price for himself, with his wife’s full knowledge, and bringing a portion of it, he laid it at the apostles’ feet. (Acts 5:2) Full knowledge is our word συνοιδα, and here it means that she was privy to the plan and agreed with it. Another way that it could be translated is collusion. It also indicates a level of knowledge that imparts responsibility. This can be seen in Acts 5:7-9 when Sapphira also died the sin unto death. By the way they died because they lied to God not because they kept the money (Acts 5:3-4).
For I am conscious of nothing against myself, yet I am not by this acquitted; but the one who examines me is the Lord. (1Cor. 4:4) Here we see συνοιδα used to describe an awareness of one’s own actions, or thoughts. This verse speaks to a life that has been examined by God’s standards and found in compliance with those standards. Note though Paul does not acquit himself but leaves that to God alone.
‘Now if a person sins after he hears a public adjuration to testify when he is a witness, whether he has seen or otherwise known, if he does not tell it, then he will bear his guilt. (Lev 5:1) συνοιδα is used here to translate the Hebrew word יָדַע (H3045); this word has several meanings but basically means to know. And we can see here that like in Acts it is a knowledge that brings with it a responsibility. In this case a legal responsibility.
I hold fast my righteousness and will not let it go. My heart does not reproach any of my days. (Job 27:6) I almost did not include this in the study, because συνοιδα in a helper word included in the Septuagint and does not directly translate the Hebrew. I decided to include it because it does convey the point of being aware of oneself; an awareness that leads Job to have a lack of reproach for his life.
οιδα and συνοιδα both describe knowledge as a level of awareness and in the case of συνοιδα that awareness brings with it a level of responsibility.
