理系（りけい、rikei）
- science stream

The Japanese word 理系 (りけい, rikei) refers to the "science and engineering" field, or more broadly, the "sciences." It’s an abbreviation, and it signifies a focus on scientific disciplines. It encompasses fields like physics, chemistry, biology, mathematics, computer science, and engineering. It's often used to distinguish between different academic or professional paths. ⚫︎ It contrasts with 文系 (bunkei), which focuses on humanities and social sciences. ⚫︎ The word emphasizes subjects involving experimentation, logical thinking, and mathematical principles. ⚫︎ 理系 indicates a direction toward careers and studies related to science, technology, engineering, and mathematics (STEM).

⚫︎ 私は理系の大学に進学したいです。 ⚫︎ Translation: I want to go to a science and engineering university. ⚫︎ 彼女は理系科目が得意です。 ⚫︎ Translation: She is good at science subjects. ⚫︎ あの人は理系の仕事に就いています。 ⚫︎ Translation: That person works in a science-related job.

You use 理系 to: ⚫︎ Describe someone's academic major (e.g., "I'm a 理系 student.") ⚫︎ Talk about someone's career path (e.g., "He works in a 理系 field.") ⚫︎ Discuss someone's interests or strengths in specific subjects (e.g., "She's good at 理系 subjects.") ⚫︎ Indicate a preference for science or engineering-related fields. ⚫︎ It is frequently used when discussing education, career choices, or aptitude for certain subjects.

⚫︎ The word 理系 is typically written in kanji and hiragana. ⚫︎ 理 (ri) means "logic, reason, science," and 系 (kei) means "system, lineage, group." ⚫︎ It’s usually written as 理系, and there aren't other common ways to write it. ⚫︎ There is no variation in the okurigana (the suffix hiragana).

⚫︎ 科学 (kagaku) - science (broader term) ⚫︎ 理工系 (rikoukei) - science and engineering (more formal)

⚫︎ 文系 (bunkei) - humanities and social sciences ⚫︎ 文科系 (bunkakei) - humanities and social sciences (more formal)

彼は理系の大学院に進学して、研究者を目指しています。 ⚫︎ Translation: He is going to graduate school in science and engineering and aims to become a researcher. ⚫︎ Explanation: This sentence demonstrates how 理系 is used in the context of academic aspirations and career goals.

私は理系の授業が好きで、特に数学と物理が好きです。 ⚫︎ Translation: I like science subjects, especially math and physics. ⚫︎ Explanation: The example shows the usage of 理系 to refer to someone's fondness for science-related subjects.

The word 理系 is a shortened form of 理科系統 (rika keitou), which means "science system/lineage." ⚫︎ 理 (ri) comes from words related to logic, reason, and scientific principle. ⚫︎ 系 (kei) denotes a system or group of subjects. The word's construction reflects a focus on scientific fields and their interconnectedness.