What is the opposite of the word delta?

The opposite of the word delta depends on which meaning of delta you are using, because delta has multiple definitions. If you are using delta in the mathematical sense meaning change or difference, the opposite would be sameness, constancy, no change, or stability. In that sense, if delta means something changed, the opposite is that it stayed the same. If you are using delta in the geographical sense meaning the mouth of a river where it spreads out and deposits sediment into the sea, the opposite would be the source or headwaters, which is where a river begins, usually in mountains or springs. So source is the geographical antonym of delta. In finance, where delta means sensitivity or exposure, the opposite could be zero delta or hedged, meaning no exposure. In the NATO phonetic alphabet, Delta means the letter D, so it has no real opposite, but another letter could be considered opposite. In terms of symbolism, where delta as a triangle pointing up means change and growth, the opposite could be stability or stagnation. Because delta does not have a single dictionary antonym like hot and cold, you must choose the opposite based on context. The most commonly accepted opposites are sameness for the change meaning and source for the river meaning.