Strongs Number: G5778
Tense - Perfect
The perfect tense in Greek corresponds to the perfect tense in English, and describes an action which is viewed as having been completed in the past, once and for all, not needing to be repeated.
Jesus' last cry from the cross, TETELESTAI ("It is finished!") is a good example of the perfect tense used in this sense, namely "It [the atonement] has been accomplished, completely, once and for all time."
Certain antiquated verb forms in Greek, such as those related to seeing (eidw) or knowing (oida) will use the perfect tense in a manner equivalent to the normal past tense. These few cases are exception to the normal rule and do not alter the normal connotation of the perfect tense stated above.