(しゅうせい)

しゅうせい
noun
nature; instinct; ingrained habit
1. nature, instinct, innate behavior
An animal's innate behavioral pattern or instinct. Used in biology and nature contexts to describe characteristic behaviors of a species.
(ねこ)には夜行性(やこうせい)習性(しゅうせい)がある。
Cats have a nocturnal nature.
(わた)(どり)習性(しゅうせい)研究(けんきゅう)している。
I'm researching the behavioral habits of migratory birds.
この昆虫(こんちゅう)(ひかり)(あつ)まる習性(しゅうせい)があり、(なつ)(よる)街灯(がいとう)(まわ)りに大量(たいりょう)()られる。
This insect has an instinct to gather around light, and large numbers can be seen around streetlights on summer nights.
2. ingrained habit, second nature
A deeply ingrained habit or behavioral tendency in a person, often one that is hard to change. Implies the behavior has become almost instinctive.
値段(ねだん)確認(かくにん)するのは職業(しょくぎょう)習性(しゅうせい)だ。
Checking prices is a professional habit of mine.
記者(きしゃ)習性(しゅうせい)で、つい質問(しつもん)してしまう。
Out of a reporter's ingrained habit, I can't help asking questions.
長年(ながねん)習性(しゅうせい)簡単(かんたん)には(なお)らないもので、引退(いんたい)しても(あさ)(はや)()()めてしまう。
Long-standing habits don't change easily — even after retirement, I still wake up early in the morning.

USAGE NOTE:
Sense 1 (animal instinct) is the primary meaning. When applied to people (sense 2), it emphasizes that the behavior is so deeply rooted it has become almost involuntary.

COMMON COLLOCATIONS:

  • 習性(しゅうせい)がある (have a habit/instinct)
  • 動物(どうぶつ)習性(しゅうせい) (animal behavior/instinct)
  • 職業(しょくぎょう)習性(しゅうせい) (professional habit)
  • 長年(ながねん)習性(しゅうせい) (long-standing habit)

SIMILAR WORDS:

  • 本能(ほんのう): instinct (more fundamental, biological drive)
  • (くせ): habit, quirk (everyday word for personal habits, often negative)
  • 習慣(しゅうかん): habit, custom (neutral, broader usage)