darner; Aeshnidae dragonfly
Specifically refers to dragonflies of the family Aeshnidae, known as darners in English. In everyday Japanese, ヤンマ often broadly means any large dragonfly.
A large darner was flying over the pond.
large dragonfly
Commonly used for any large dragonfly, not strictly limited to Aeshnidae. Often appears in children's speech and nature observation.
In summer, large dragonflies often come to our garden.
The children are chasing a large dragonfly.
Usually written in katakana; usually written in kana.
Hiragana spelling, also common.
Rare kanji spelling; the first character is a variant of 蜻蛉.
Contains outdated kanji usage; not recommended for modern writing.
The origin is uncertain. Possibly related to the mimetic word やんやん describing a buzzing sound, or from an old compound meaning 'large horsefly'.