The New Testament was written in Koine Greek — the everyday common language of the first century. Understanding key Greek concepts unlocks deeper meaning in Scripture. Words like agape (love), charis (grace), and logos (word) carry far richer meaning than English translations capture.

Greek nouns change form based on their role in a sentence:
Nominative — the subject (who is acting)
Genitive — possession (of, belonging to)
Dative — indirect object (to, for)
Accusative — direct object (receives the action)

Greek verb tenses convey more than time — they show the kind of action:
Present — ongoing, continuous action
Aorist — simple, punctiliar action (happened once)
Perfect — past action with present results (John 19:30 "It is finished" — tetelestai — perfect tense: permanently completed)
Imperfect — continuous action in the past

Agape (ἀγάπη) — unconditional, sacrificial love. Used for God's love in John 3:16.
Phileo (φιλέω) — warm affection, friendship love. Used when Jesus wept — John 11:36.
Eros (ἔρως) — romantic love. Not used in the New Testament, but present in Greek culture.

When Jesus asked Peter "Do you love me?" (John 21), He used agape. Peter replied with phileo. The conversation reveals Peter's honest self-assessment before restoration.

Hamartia (ἁμαρτία) — sin, missing the mark
Dikaiosyne (δικαιοσύνη) — righteousness, justice
Soteria (σωτηρία) — salvation, deliverance
Ekklesia (ἐκκλησία) — church, assembly, called-out ones
Parousia (παρουσία) — presence, coming — used for Second Coming
Pneuma (πνεῦμα) — spirit, breath, wind — the Holy Spirit
Sarx (σάρξ) — flesh, human nature in its weakness