In the phonetic alphabet, Delta represents the letter D. According to my American Heritage Dictionary (1969), delta is also 1. The fourth letter of the Greek Alphabet Δδ 2. A usually triangular alluvial deposit at the mouth of a river 3. Anything resembling the shape of a triangle 4. In Mathematics A finite increment in a variable.
A delta ray is 1. An electron ejected (weeeeee!!!) from matter by ionizing radiation 2. The track of such an electron in a nuclear emulsion or cloud-chamber photograph.
A delta wing is an aircraft with sweptback wings that give it the appearance of an isosceles triangle.
But some of you might like this Delta best...