菱 - diamond (shape), water chestnut, rhombus

rhombus-shaped mochi

caltrop

Trapa incisa (species of plant closely related to the water caltrop)

water chestnut flower; water caltrop flower

Takebishi Electric Sales Corporation

Mitsubishi Heavy Industries

flower-shaped family crest

Red Crystal (politically and religiously neutral emblem used by the International Committee of the Red Cross)

rhombencephalon; hindbrain

large Japanese junk

groundhopper (esp. species Tetrix japonica)

rhombohedron