noun-modifying (irregular)
nine-year; novennial; recurring every nine years
Used attributively before nouns like 計画 (plan) or 事業 (project) to indicate a span or recurrence of nine years. Formal, often found in official documents and statistics.
九カ年計画の最終年度です。
This is the final year of the nine-year plan.
この調査は九カ年にわたって行われた。
This survey was conducted over a period of nine years.
Arabic numeral variant, common in tables and lists.
Arabic numeral with small ヵ.
Arabic numeral with small ヶ.
Arabic numeral with hiragana か.
Arabic numeral with kanji 箇, very formal.
Arabic numeral with full-size katakana ケ.
九年 is the simple noun 'nine years', while 九カ年 is a prenominal adjective form used before another noun, often in formal contexts.
Compound of 九 (nine) + カ (counter for years, from 箇) + 年 (year). The カ is a simplified form of the counter 箇, commonly used in time spans.