noun-modifying (irregular)
septennial; recurring every seven years
Used attributively to describe plans, events, or periods that occur or last for seven years. Common in official contexts like 七カ年計画 (seven-year plan).
政府は新たな七カ年計画を発表した。
The government announced a new seven-year plan.
この七カ年調査の結果がまとまった。
The results of this septennial survey have been compiled.
Variant with large ケ, sometimes seen.
Arabic numeral with small ヶ.
Arabic numeral with katakana ヵ.
Arabic numeral with hiragana か.
Arabic numeral with large ケ.
七年 is the simple noun meaning 'seven years', while 七カ年 is used attributively to modify nouns, often in formal or statistical contexts.
Compound of 七 (seven) + カ年 (counter for years). The カ is a counter marker derived from 箇, a classical counter word. The reading ななかねん uses the native Japanese number reading.