noun
dolphin; small toothed whale
Refers to dolphins and similar small toothed whales such as porpoises and belugas. The katakana spelling イルカ is most common.
水族館でイルカのショーを見た。
I saw a dolphin show at the aquarium.
イルカはとても賢い動物だ。
Dolphins are very intelligent animals.
Hiragana spelling is also common.
クジラ refers to whales in general, especially larger baleen whales, while イルカ refers to smaller toothed whales.
The origin is uncertain; the kanji 海豚 (sea pig) is a jukujikun reading. The word is native Japanese.