noun
prosperous period; heyday; peak
Refers to a time when something is at its height of prosperity, activity, or influence. Often used in historical or business contexts.
この町は江戸時代に商業の盛期を迎えた。
This town reached its commercial heyday during the Edo period.
彼の作家としての盛期は短かった。
His peak as a writer was short.
Compound of 盛 (prosperous, flourishing) and 期 (period, time). The reading せいき is the standard on'yomi for both characters.