A diamond (the gemstone); a very hard gem commonly used in jewelry like rings.
彼は婚約指輪にダイヤモンドを選んだ。
He chose a diamond for the engagement ring.
ダイヤモンドは硬い宝石だ。
Diamonds are hard gemstones.
このダイヤはとても高価だ。
This diamond is very expensive.
In baseball, the diamond: the infield area or the baseball field's diamond-shaped area.
野球場のダイヤモンドはきれいに整備されている。
The baseball diamond at the stadium is well maintained.
ダイヤでの守備が試合の勝敗を分けた。
Defense on the diamond decided the game's outcome.
The diamonds suit in playing cards (♦).
トランプでダイヤのAを引いた。
She drew the Ace of diamonds in the card game.
手札にダイヤが多いと不利になることもある。
Having many diamonds in your hand can sometimes be disadvantageous.