Several parts combine into one character.

街 is a phonetic-semantic compound: 行 (the "walk-cross" radical, originally a pictograph of a four-way intersection where two roads cross) wrapped around 圭 (guī, "jade tablet" — providing the sound). The 行 radical preserves its original "intersection" meaning beautifully here: 街 captures the concept of busy streets where people move and crisscross. From this concrete urban scene grew "street, city avenue, busy commercial road."

Korean reading "ga." 街路 (garo, street / urban avenue), 商街 (sangga, shopping street / commercial district), 街道 (gado, highway), 繁華街 (beonhwaga, downtown / bustling commercial district), 街頭 (gadu, street corner — used in 가두시위 "street demonstration"). Korean urban vocabulary draws from 가.

Mandarin jiē, 1st tone. 街 (jiē, street), 街道 (jiēdào, street), 上街 (shàngjiē, "to go onto the street" = to go out shopping / browsing), 街头 (jiētóu, street corner — used in 街头艺人 "street performer"), 步行街 (bùxíngjiē, "walk-only street" = pedestrian street — major Chinese cities have famous pedestrian shopping streets like Beijing's 王府井步行街 and Shanghai's 南京路步行街).

Japanese on-readings: ガイ (gai) — 商店街 (shōtengai, "shop-store-street" = covered shopping arcade — a defining feature of Japanese urban geography; nearly every Japanese train station neighborhood has its own shōtengai with mom-and-pop shops, grocery stalls, and izakaya). カイ (kai) — 街道 (kaidō, "street-road" = old highways). Kun-reading まち (machi) — 街 (machi, urban street / shopping district). Critical homophone caution: まち is also written 町 (different kanji, same kana) for "town" — but 街 implies a busy commercial street, while 町 is an administrative subdivision. Tokyo's 商店街 are 街 (busy commerce), while administrative 町 names (千代田町, 中央町) are 町 (formal town divisions).

Memory aid: an intersection of roads (行) + 圭 (sound) — where streets cross = the busy commercial avenue.