外来種（がいらいしゅ、gairaいshu）
- exotic species

The Japanese word 外来種 (がいらいしゅ) refers to "invasive species" or "alien species." It describes any species of plant, animal, fungus, or microorganism that is introduced to an environment where it does not naturally occur and which causes or is likely to cause economic or environmental harm, or harm to human health. It essentially means a species that is not native to a particular area but has been introduced there, often by human activity. The definition focuses on the introduction to a new area and the subsequent negative impact. The term can be applied to both plants and animals. The 外来種 has the potential to outcompete native species, disrupt ecosystems, and spread diseases.

⚫︎ 日本には、特定外来種の駆除を目的とした法律があります。 Translation: In Japan, there are laws aimed at eradicating specific invasive species. ⚫︎ この湖には、多くの外来種の魚が生息しています。 Translation: Many invasive fish species live in this lake. ⚫︎ 外来種の植物が在来種を駆逐している。 Translation: Invasive plant species are driving out native species.

This word is used in a formal to semi-formal context. You might encounter it in scientific discussions, environmental reports, news articles, or conversations about conservation and ecology. You would use 外来種 when discussing the impact of non-native species on the environment, the control or management of these species, or the laws and regulations related to them. This word is typically not used in casual conversations, such as when you talk about your pet, or an animal in the zoo, that are not considered "invasive" in the first place.

This word is written in kanji as 外来種, with the reading がいらいしゅ in hiragana. There are no other ways to write the word and no variations in the okurigana.

There aren't many direct synonyms, as 外来種 is a specific technical term. However, you could sometimes use: ⚫︎ 侵略的外来種 (しんりゃくてきがいらいしゅ) - invasive alien species (more emphasis on the invasive aspect). ⚫︎ 非在来種 (ひざいらいしゅ) - Non-native species (this is a more general term and less strong than 外来種).

⚫︎ 在来種 (ざいらいしゅ) - native species.

この公園では、外来種の駆除作業が行われています。 ・Translation: Eradication work for invasive species is being carried out in this park. ・Explanation: This sentence describes the action of removing invasive species, showing a practical application of the term.

外来種の影響で、地域の生態系が変化しています。 ・Translation: The ecosystem of the area is changing due to the impact of invasive species. ・Explanation: This sentence explains that 外来種 have had a negative impact on the local ecosystem.

The word is a combination of: ⚫︎ 外 (がい) - "outside," "foreign," or "external." ⚫︎ 来 (らい) - "come," or "arrival." ⚫︎ 種 (しゅ) - "species," or "kind." Therefore, 外来種 literally means "outside-arriving species," which accurately reflects the meaning of introduced species.