epangelia

At its core this word names a promise, and in the New Testament it almost always names God's promise. It points to a commitment freely made and meant to be kept, and the weight of the word is that the one who makes it is faithful, so the promise is as good as done. The Bible ties it again and again to Abraham: God swore to bless him and his descendants, and the whole story of salvation is the slow keeping of that one pledge.

The word lives in two closely joined shades. Sometimes it stresses the act and the standing pledge itself, the word God gave and will not take back, the thing believers wait for and rely on. Other times it slides to the thing promised, the actual gift named in the pledge, so that people are said to receive the promise, inherit the promise, or be given the promise of the Spirit. The line between the pledge and the gift is often soft, because to trust the pledge is to count on the gift.

What holds the two shades together, and what makes this one word rather than two, is that both rest on the same act: someone has bound himself to do good for another, and that other now leans his whole future on it. Whether the focus falls on the pledging word or on the blessing pledged, the heart of the word is a future secured by a faithful giver.

Once, the word steps outside its usual religious setting and means a plain human agreement. When a band of men plots to ambush Paul, they are described as ready to act once they have the consent, the go-ahead, from the official they are pressing. Here the word is not God's saving pledge at all but the ordinary sense of giving one's word to a scheme.

This is the same basic idea of binding oneself by a promise, but pointed at a human transaction rather than a divine gift, which is why a reader needs a different English word for it. Most translations render it agreement, consent, or assent rather than promise.