also: ぐさ
noun, noun, used as a suffix
Used as a noun or suffix to indicate the source, cause, or origin of something. Often appears in compounds with the voiced form ぐさ.
彼の失敗は村中の語り種になった。
His failure became the talk of the whole village.
彼の慌てぶりはみんなの笑い種になった。
The way he panicked became a source of amusement for everyone.
noun
Refers to a type, variety, or kind of something. Often used in the pattern 〜の種.
クジラは哺乳動物の一種だ。
A whale is a kind of mammal.
種々の品が棚に並んでいる。
Goods of various kinds are lined up on the shelves.
noun, counter
counter for varieties
Counter used for types or varieties of things. Commonly used with numbers to count different kinds.
三種の宝物は三種の神器とも呼ばれる。
The three sacred treasures are also called the three imperial regalia.
五種の供物を神前に供えた。
They offered five kinds of offerings before the deity.
原因 is a more formal and direct word for 'cause', while 種 often carries a nuance of a latent or underlying source.
種類 is the standard word for 'kind' or 'type', while 種 is more literary or used in compounds and counters.
The kanji 種 is used for its meaning of 'seed' or 'kind'. The reading くさ is a native Japanese word, possibly related to 草 (くさ, grass) in the sense of 'origin' or 'source', but the exact derivation is uncertain.