Meaning
The kanji 湖 means "lake." You'll encounter it in place names, travel writing, and nature descriptions — most famously in 琵琶湖 (Lake Biwa), the largest freshwater lake in Japan.
湖 is a phono-semantic compound (形声文字 — けいせいもじ). On the left is 氵 (さんずい), the "water" radical — the same one found in 海 (sea), 川 (river), and 池 (pond). It marks the kanji as water-related.
On the right is 古 (ふるい), meaning "old" or "ancient." It contributes the "ko" sound and quietly suggests age — lakes are, after all, among the oldest features of any landscape, shaped over millennia.
湖 has 12 strokes and is classified as Grade 4. Once you see the two components clearly, it's easy to hold in memory. It appears on the JLPT N3 list.
Readings
On'yomi (音読み) — Chinese-derived readings
The on'yomi reading is コ (ko). It appears mainly in compound words, especially in formal or technical vocabulary.
コ (KO):
湖畔 (kohan) — lakeside. Describes the land bordering a lake: 湖畔の公園 (kohan no kōen) means "lakeside park."
湖水 (kosui) — lake water. Common in environmental writing: 湖水の透明度 (kosui no tōmeido) means "the clarity of the lake water."
湖沼 (koshō) — lakes and marshes. A collective term for inland bodies of water, often used in ecology: 湖沼の生態系 (koshō no seitaikei) — "lake and marsh ecosystems."
Kun'yomi (訓読み) — Native Japanese readings
The kun'yomi reading is みずうみ (mizuumi). This is the everyday word for "lake" in Japanese — the form you'll use in conversation and plain writing.
みずうみ (mizuumi):
湖 (mizuumi) — lake. For example: 美しい湖 (utsukushii mizuumi) — "a beautiful lake."
琵琶湖 (Biwako) — Lake Biwa. Japan's largest freshwater lake, in Shiga Prefecture. Here 湖 reads as こ (on'yomi), a pattern common in lake place names.
湖のほとり (mizuumi no hotori) — lakeshore. Similar to 湖畔, but more poetic in tone — the kind of phrase you'd find in a novel rather than a guidebook.
Common Words & Compounds
Common words using 湖, grouped by theme.
Nature & Geography
- 湖畔 (kohan) — Lakeside, shore of a lake.
- 湖水 (kosui) — Lake water. Often used in scientific or environmental contexts.
- 湖面 (komen) — Lake surface.
- 湖底 (kotei) — Lake bottom.
- 湖岸 (kogan) — Lake shore or bank. Suggests a slightly more rugged edge than 湖畔.
- 湖沼 (koshō) — Lakes and marshes.
- 湖上 (kojō) — On the lake. Used for activities taking place on the water, such as boating or fishing.
Place Names & Specific Lakes
- 琵琶湖 (Biwako) — Lake Biwa. Japan's largest lake, in Shiga Prefecture.
- 洞爺湖 (Tōyako) — Lake Toya. A caldera lake in Hokkaido, known for its hot springs and the 2008 G8 Summit.
- 富士五湖 (Fuji goko) — Fuji Five Lakes. A cluster of five lakes at the northern base of Mount Fuji.
Phrases & Activities
- 湖畔の町 (kohan no machi) — Lakeside town.
- 湖畔を散歩する (kohan wo sanpo suru) — To stroll along the lakeside.
- 湖を眺める (mizuumi wo nagameru) — To gaze at the lake.
- 湖で泳ぐ (mizuumi de oyogu) — To swim in the lake.
Example Sentences
湖はとても広いです。
Mizuumi wa totemo hiroi desu.
The lake is very wide.
私たちは湖のほとりでピクニックをしました。
Watashitachi wa mizuumi no hotori de pikunikku wo shimashita.
We had a picnic by the lake.
早朝の湖面は穏やかで美しかった。
Sōchō no komen wa odayaka de utsukushikatta.
The lake surface at dawn was calm and beautiful.
夏には、この湖でボートを楽しむことができます。
Natsu ni wa, kono mizuumi de bōto wo tanoshimu koto ga dekimasu.
In summer, you can enjoy boating on this lake.
山々が湖に映り、まるで絵のような景色でした。
Yamayama ga mizuumi ni utsuri, marude e no yō na keshiki deshita.
The mountains were reflected in the lake — a scene straight out of a painting.
私たちの町は、美しい湖の近くにあります。
Watashitachi no machi wa, utsukushii mizuumi no chikaku ni arimasu.
Our town sits near a beautiful lake.
冬には湖が凍り、スケートをすることができます。
Fuyu ni wa mizuumi ga kōri, sukēto wo suru koto ga dekimasu.
In winter the lake freezes over, and you can skate on it.
彼は湖の深いところで釣りをしています。
Kare wa mizuumi no fukai tokoro de tsuri wo shite imasu.
He is fishing in the deep part of the lake.
夕日が湖に沈む景色は感動的でした。
Yūhi ga mizuumi ni shizumu keshiki wa kandōteki deshita.
Watching the sun sink into the lake was breathtaking.
Memory Tip
Picture the kanji as "water" (氵) beside something "old" (古). Lakes are ancient — still and deep, shaped long before any town appeared beside them. When you see those three water drops next to 古, think: old water, settled over centuries into a lake.