気体（きたい、kitai）
- gas

The Japanese word 気体 (気体) means "gas" or "gaseous substance" in English. It refers to one of the three fundamental states of matter (the others being solid and liquid). A gas has no definite shape or volume and can expand to fill any available space. The word 気体(気体) describes substances where the molecules are widely dispersed and move freely. It’s also used to classify elements and compounds that exist in the gaseous state under normal conditions.

⚫︎水素は気体です。 Translation: Hydrogen is a gas. ⚫︎空気に含まれる酸素は気体です。 Translation: The oxygen contained in the air is a gas. ⚫︎この化学反応によって二酸化炭素の気体が発生しました。 Translation: A gas of carbon dioxide was produced by this chemical reaction.

You use 気体 (気体) when discussing gases in scientific contexts, describing the state of a substance, or referring to gases in general. It's suitable for both formal and informal conversations. For example, you might use it in a chemistry class or when discussing the properties of air or other substances that exist as gases.

The word 気体 (気体) is written using the kanji 気 (ki) meaning "spirit", "mind", or "atmosphere", and 体 (tai) meaning "body" or "substance". The reading is きたい (kitai) in hiragana. There are no other common ways to write this word. Okurigana is not applicable for this word.

There are no perfect synonyms for 気体 (気体) as it's a specific term for the state of matter. However, depending on the context, you could use related terms like: ⚫︎ガス (gasu): which is a direct borrowing from English, commonly used in everyday language.

The antonyms, which describe the opposite states of matter, are: ⚫︎固体 (kotai): solid. ⚫︎液体 (ekitai): liquid.

窒素は常温で無色無臭の気体です。 ・Translation: Nitrogen is a colorless and odorless gas at room temperature. ・Explanation: This sentence describes the properties of nitrogen, specifying it as a gas.

気体は温度が上がると膨張する。 ・Translation: Gas expands when the temperature rises. ・Explanation: This sentence explains a characteristic behavior of gases, linking it with temperature changes.

The word 気体 (気体) combines 気 (ki), which historically represented the "essence" or "energy" that gives form to matter, and 体 (tai), meaning "body" or "substance." Thus, 気体 (気体) originally referred to a substance that takes on a form based on a certain essential "spirit" or "energy" or "essence." This meaning has evolved to refer to the gaseous state of matter.