Meaning
The kanji 汽 (ki) primarily means steam or vapor. This core meaning is evident in its visual structure and etymology. It also broadly refers to things powered by steam, particularly the locomotive or steamboat, and processes involving the evaporation or gaseous forms of water.
汽 is a phono-semantic compound (形声文字 - keisei moji). The left-hand radical, 氵 (さんずい - sanzui), is the 'water' radical, signifying the kanji's connection to water. The right-hand component, 气 (き - ki), serves as the phonetic component, providing the 'ki' reading, and subtly contributing to the meaning of 'gas' or 'air'. Together, these components clearly convey the image of water transforming into a gaseous state—steam.
Visually, you can imagine the three drops of water (氵) on the left heating up and changing into the cloud-like form of gas or air (气) on the right. This vividly illustrates the concept of steam rising. This intuitive connection makes the kanji's meaning quite clear once its components are understood.
The kanji 汽 has 6 strokes and is a Jōyō Kanji. It is typically encountered at the N1 level of the JLPT, reflecting its use in more specific or technical vocabulary.
Readings
On'yomi (音読み) — Chinese-derived readings
The primary, and almost exclusive, on'yomi reading for 汽 is キ (KI). Derived from ancient Chinese pronunciation, this reading is consistently used in most kanji compounds containing 汽. It's crucial for understanding technical terms and names of steam-powered vehicles or related concepts.
汽車 (kisha) — This is one of the most common and recognizable compounds. It directly means 'steam locomotive' or, more broadly, 'train'. While it specifically refers to trains powered by steam engines, it can also refer to any train in modern contexts. For example, 昔の子供たちは、汽車の音が聞こえると喜んだ。(Mukashi no kodomotachi wa, kisha no oto ga kikoeru to yorokonda. - Children in the past were delighted when they heard the sound of a train.)
汽船 (kisen) — Meaning 'steamboat' or 'steamship'. Like 汽車, this term refers to water vessels propelled by steam power. For instance, 港には大きな汽船が停泊していた。(Minato ni wa ookina kisen ga teihaku shite ita. - A large steamboat was anchored in the port.)
汽笛 (kiteki) — This compound translates to 'steam whistle' or 'siren', referring to the distinctive sound made by a steam-powered train or ship. For example, 夜、遠くで汽笛が鳴った。(Yoru, tooku de kiteki ga natta. - At night, a steam whistle blew in the distance.)
汽水 (kisui) — This specific term means 'brackish water'. It refers to water saltier than freshwater but less salty than seawater, often found in estuaries where rivers meet the sea. For example, 汽水には独特の生態系がある。(Kisui ni wa dokutoku no seitaikei ga aru. - Brackish water has a unique ecosystem.)
Kun'yomi (訓読み) — Native Japanese readings
The kanji 汽 does not have any commonly used native Japanese kun'yomi readings. It functions almost exclusively within compounds using its on'yomi, キ, often relating to steam-powered mechanisms or the steam itself. This is common for many kanji introduced primarily for specific technical or conceptual meanings that lacked direct native Japanese verb or adjective equivalents. Therefore, you won't encounter 汽 used alone with a kun'yomi reading in modern Japanese.
Common Words & Compounds
The kanji 汽 is frequently found in words related to steam, water states, and historical or industrial machinery. Understanding these compounds is essential for grasping the full scope of 汽's usage.
Transportation & Industrial Machinery
汽車 (kisha) — steam locomotive, train. A classic example of steam-powered transport.
汽船 (kisen) — steamboat, steamship. Historical and modern vessels powered by steam.
汽笛 (kiteki) — steam whistle, siren. The characteristic sound device of steam engines and ships.
汽油 (kiyu) — gasoline, petrol. An older, more technical term for fuel used in internal combustion engines, implying a volatile 'vapor oil'.
汽罐 (kikan) — boiler. A vessel used for heating water to generate steam, particularly in steam engines.
汽力発電 (kiryoku hatsuden) — steam power generation. The process of generating electricity using steam turbines.
Steam & Water States
蒸気 (jōki) — steam, vapor. This crucial compound combines 汽 with 蒸 (steam, evaporate) to express its fundamental meaning.
水蒸気 (suijōki) — water vapor, steam. A more specific term for steam, explicitly emphasizing its origin from water.
汽水 (kisui) — brackish water. Water that is a mix of fresh and saltwater, often found in estuaries.
汽水域 (kisuiiki) — brackish water area, estuary. Geographical areas where brackish water is found.
汽水湖 (kisuiko) — brackish lake. A lake containing brackish water.
排汽 (haiki) — exhaust steam. Steam that has been used and is expelled from an engine.
吸汽 (kyūki) — intake steam/vapor. The process of drawing in steam or vapor, for example, into an engine.
Example Sentences
昔は汽車が主要な交通手段でした。
Mukashi wa kisha ga shuyō na kōtsū shudan deshita.
In the past, steam locomotives were the primary means of transportation.
港には大きな汽船が停泊していた。
Minato ni wa ookina kisen ga teihaku shite ita.
A large steamboat was anchored in the port.
列車の汽笛が遠くから聞こえてきた。
Ressha no kiteki ga tooku kara kikoete kita.
The train's whistle was heard from afar.
鍋から熱い蒸気が立ち上がる。
Nabe kara atsui jōki ga tachiagaru.
Hot steam rises from the pot.
この湖は汽水湖なので、淡水魚と海水魚が混在しています。
Kono mizuumi wa kisuiko nanode, tansuigyo to kaisuigyo ga konzai shite imasu.
Because this is a brackish lake, both freshwater fish and saltwater fish coexist.
蒸気機関車は石炭を燃やして汽力を得る。
Jōki kikansha wa sekitan wo moyashite kiryoku wo eru.
Steam locomotives obtain power by burning coal.
古い汽油エンジンは、今ではほとんど見かけなくなった。
Furui kiyu enjin wa, ima de wa hotondo mikakenaku natta.
Old gasoline engines are rarely seen anymore.
汽水域は豊かな生態系を持つ場所だ。
Kisuiiki wa yutakana seitaikei wo motsu basho da.
Brackish water areas are places with rich ecosystems.
加湿器から細かい水蒸気が噴射されている。
Kashitsuki kara komakai suijōki ga funsha sarete iru.
Fine water vapor is being sprayed from the humidifier.
温泉地では、地中から豊富な蒸気が噴き出しているのを見ることができる。
Onsenchi de wa, chichū kara hōfu na jōki ga fukidashite iru no wo miru koto ga dekiru.
In hot spring areas, you can see abundant steam gushing out from underground.
Memory Tip
To remember 汽, start by visualizing its components: the 'water' radical (氵) on the left and the 'gas/air' component (气) on the right. Imagine water boiling rapidly, with the three drops on the left literally transforming into the 'air' or 'gas' on the right, creating steam. This vivid image of water turning into vapor serves as a powerful mnemonic for remembering that 汽 means 'steam' or 'vapor'. Additionally, connect it to 'steam locomotive' (汽車) as a concrete example of this concept.