Perhaps The Prince Should Sort Them Out.
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21A intercept between fixed point and foot of an ordinate ?? A_S_E_S_
No best answer has yet been selected by pats. Once a best answer has been selected, it will be shown here.
For more on marking an answer as the "Best Answer", please visit our FAQ.The answer word derives from latin linea abscissa, which means a line cut off.
I have never seen abscisse or absciss used but would not dispute them.
I would however say that however many variants are acceptable the most common one is abscissa and I would imagine that it would be the one used in the formal solution, when it appears.
Sorry if this sounds pedantic; I am really just throwing in my threepenny worth.