Words from the Greek and Hebrew that carry more freight than any single English rendering can hold. Each entry is what the word meant in ordinary use, what it does in Scripture, and where to read it.
apologia
a defense, a reasoned answer
A formal, reasoned reply, the kind a defendant gives in court. It is not an apology in the modern sense of expressing regret. When Peter tells believers to be ready to give an apologia for their hope, he is asking for a case, made with gentleness and respect, not a mood.
Where to read it
ekklēsia
assembly, gathering, congregation, church
In ordinary Greek an ekklēsia was simply a summoned assembly, the body of citizens called together to transact public business. There is nothing religious in the word itself, and Scripture uses it that way: the rioting crowd in the theater at Ephesus is an ekklēsia three times over, and the city clerk tells them to take their grievance to the regular assembly instead.
The Septuagint had already put the word to covenantal use, rendering the Hebrew qahal, the assembled congregation of Israel. That is the sense the New Testament inherits, and Hebrews makes the continuity explicit by quoting Psalm 22:22 with ekklēsia on Christ’s lips: he sings God’s praise in the midst of the congregation.
In the New Testament it works at two scales. It names a particular congregation in a particular place, including one small enough to meet in a house, and it names the whole body of the redeemed under Christ as head. Both are ordinary usage, and context decides which is in view.
It rarely stands alone
Because the noun carries no Christian content of its own, the New Testament almost always says which assembly it means. The qualifier can name the owner, the church of God at Corinth, or the place, the church in Corinth, or the people themselves, the church of the Thessalonians. It pluralizes just as readily: Paul writes to the churches of Galatia, relays greetings from all the churches of Christ, and holds up the churches of God in Judea as the pattern the Thessalonians followed. One word has to cover a single congregation, a region full of them, and a pagan town meeting, so the qualifier is doing real work. Where it does stand bare, the context has already named the assembly in view, as in Ephesians 5, where the one who loves it is Christ.
A caution on etymology
The popular gloss “the called-out ones,” built from ek (out of) plus kaleō (to call), preaches well and is not how the word functions. Etymology is not meaning. A word means what its users use it to mean, and by the first century ekklēsia meant assembly, which is why a pagan mob in Ephesus qualifies. The doctrine of a people called out of the world is thoroughly biblical, but it rests on passages that teach it, not on the parts of this noun.
Where to read it
Related
Lexical data follows Strong’s numbering; occurrence counts are the New Testament totals given in Strong’s concordance and vary slightly with the underlying text. Definitions are my own summaries, checked against standard lexicons.