The Greek verb epistamai means to know, to understand thoroughly, or to be well acquainted with something. Unlike ginosko (relational knowing) or oida (innate knowing), epistamai emphasizes practical knowledge from engagement — expertise or understanding gained through experience.
In Acts, epistamai is used when people recognize Paul's authority (Acts 19:15 — 'Jesus I know, and Paul I know'), when someone possesses real expertise, and when knowledge is required for proper judgment. It marks the difference between familiarity and genuine understanding.
Theologically, epistamai points to the kind of knowledge that results from deep engagement with truth. Biblical knowing is not merely intellectual but experiential — knowing God means walking with Him, not merely knowing about Him.