～代 | Grammar

Structure

Number (multiple of 10) + 代　– age decade (e.g., 20代, 30代)

Number + 年代　– historical decade/era (e.g., 1990年代)

[noun (age decade)] + 代 + の + [noun]
[noun (age decade)] + 代 + で
[noun (age decade)] + 代 + 前半/半ば/後半

Description

The suffix ～代 (だい) is attached to numbers to express age ranges (decades of life) or historical decades (time periods). It is one of the most common ways to talk about approximate ages or eras in Japanese.

Age decades

When attached to a multiple of ten, ～代 indicates "one's ___ties" – the range of ages within that decade.

じゅうだい10代 – teens (10–19)
にじゅうだい20代 – twenties (20–29)
さんじゅうだい30代 – thirties (30–39)

。

She is a student in her twenties.

。

My father quit his company in his fifties.

You can further narrow the range with 前半 (first half), 後半 (second half), 半ば (mid-), or 初め (early) / 終わり (late):

。

He is in his late thirties.

Historical decades

When attached to a year number with 年, ～年代 indicates a historical decade (e.g. "the 1990s").

。

This song was popular in the 1980s.

、。

The internet spread after entering the 2000s.

Notes

Be careful not to confuse ～代 (だい) meaning "decade/age range" with ～代 (だい) meaning "fee" or "cost" (e.g. でんわだい電話代 = phone bill, しょくじだい食事代 = meal cost). The reading is the same, but the usage and meaning are different.

Examples

。

I want to study abroad while I'm in my twenties.

、。

When I was a teenager, I played soccer every day.

、。

My mother is in her forties, but she is very energetic.

。

That actor looks like he's in his early thirties.

。

My grandfather continues to take walks even in his eighties.

。

I like music from the 1990s.

。

This building was built in the 1960s.

。

She got married in her mid-twenties.

。

This is a smartphone that is easy to use even for people in their sixties.

きごう？

What decade (of age) are you in?

えすえぬえすSNSだっ。

The 2010s were an era when social media changed dramatically.

、。

After reaching my late fifties, I started paying more attention to my health.

References

代Bunpro