Pronunciation: (del'tu),[key] —n. 1. the fourth letter of the Greek alphabet (Δ, δ).
2. the consonant sound represented by this letter.
3. the fourth in a series of items.
4. anything triangular, like the Greek capital delta (Δ).
5. Math.an incremental change in a variable, as Δ or δ.
6. a nearly flat plain of alluvial deposit between diverging branches of the mouth of a river, often, though not necessarily, triangular: the Nile delta. 7. (usually cap.) a word used in communications to represent the letter D. 8. (cap.) Astron.a star that is usually the fourth brightest of a constellation: The fourth brightest star in the Southern Cross is Delta Crucis.
Pronunciation: (del'tu),[key] —n.Mil. the NATO name for a class of Soviet nuclear-powered ballistic missile submarine armed with 16 multi-warhead missiles.