It’s better known by its stage name, diamond.
A square is a rectangle, but a rectangle isn’t necessarily a square
Same with rhombus and diamond
A rhombus is a diamond, but a diamond isn’t necessarily a rhombus
Rhombus has to have four equal sides, a diamond does not.
I think most people would say a 2D shape that they’d call a diamond would have 4 equal sides.
I don’t think very many at all would call an elongated parallelogram a “diamond”.
If I took a traditional diamond shape and elongated just the bottom sides.
I feel like most would call it a diamond still. Specific term would be a kite. Many wouldn’t come up with that, though. It’s not an elongated parallelogram. It is not a rhombus.
“Diamonds” on bicycle playing cards have curved edges. They are not a rhombus because sides are not parallel. Most agree that it’s the classic diamond shape, though.
For me the shape I was thinking of was if you take a simplified 2D version of this 💎, with there being 4 sides, 2 pairs of equal sides but not 4 equal sides
I imagine what people are talking about here is this ♦️ sort of diamond.
I blame me not being a native speaker for thinking of diamon diamond