How to say "era" in Japanese

• 時代じだいJLPT N4approx.Common
  nounThe general word for an era or age — a stretch of history with a character of its own, or a period of a person's life, as in 'the Edo era' or 'the computer age'.
  今いまや時代じだいとの競争きょうそうになった。↗

  It was now a race against time.
• 紀元きげんCommon
  nounAn era only in the calendrical sense: the epoch from which years are counted, as in 'the Christian era'. It is not used for spans of history; for those, 時代 is the word.
• 年代ねんだいJLPT N3approx.Common
  nounA stretch of time identified by its dates, often a decade, or the period something belongs to. For 'era' it fits date-defined spans like 'the 1980s' rather than named historical ages.
  １９９０年ねん代だいは湾岸わんがん戦争せんそうで始はじまった。↗

  The 1990s began with the Gulf War.
• 世紀せいきJLPT N3approx.Common
  nounReally 'century': a span of one hundred years, as in 'the twentieth century'. It covers 'era' only in that counting sense, not for a historical age in general.
• ピリオドCommon
  nounA loanword for a bounded period of time; it can stand in for 'era' in that sense, but it also means the punctuation mark, so for historical ages 時代 is the safer choice.

Use 時代 for a historical age or a period of life, 年代 for a date-defined span like a decade, 「ピリオド」 for a bounded stretch of time; 世紀 means century, and 紀元 the epoch from which years are counted.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 時代じだいperiod
• 紀元きげんera
• 年代ねんだいage
• エイジage
• 防御率ぼうぎょりつearned run average
• 世よage
• 世紀せいきera
• ピリオドperiod (of time)
• 代だいera