Editing Polyiamond (section)

{{short description|Polyform whose base form is an equilateral triangle}}
{{redirect|Triamond|the crystal structure|Laves graph}}
{{Commons category|Polyiamonds}}
A '''polyiamond''' (also '''polyamond''' or simply '''iamond''', or sometimes '''triangular polyomino'''<ref>{{cite web |url=https://oeis.org/A000577 |title=A000577 |last=Sloane |first=N.J.A. |date=July 9, 2021 |website=OEIS |publisher=The OEIS Foundation Inc. |access-date=July 9, 2021 |quote="triangular polyominoes (or triangular polyforms, or polyiamonds)"}}</ref>) is a [[polyform]] whose base form is an [[equilateral triangle]]. The word ''polyiamond'' is a [[back-formation]] from ''[[diamond]]'', because this word is often used to describe the shape of a pair of equilateral triangles placed base to base, and the initial 'di-' looks like a [[Greek language|Greek]] prefix meaning 'two-' (though ''diamond'' actually derives from Greek '' ἀδάμας'' - also the basis for the word "adamant"). The name was suggested by recreational mathematics writer Thomas H. O'Beirne in ''New Scientist'' 1961 number 1, page 164.