ヶ月

The counter 〜ヶ月（〜かげつ） is essential for discussing schedules, study durations, or ages of infants.

1. Pronunciation and Numbers:
Because the counter starts with a か sound, certain numbers 'double' the consonant:

• 0 months: 0ヶ月（ゼロかげつ） - used to track a newborn's age (生後0ヶ月)
• 1 month: 一ヶ月（いっかげつ）
• 6 months: 六ヶ月（ろっかげつ）
• 8 months: 八ヶ月（はっかげつ / はちかげつ）
• 10 months: 十ヶ月（じっかげつ / じゅっかげつ）
• 11 months: 十一ヶ月（じゅういっかげつ） - showing that the phonetic change applies to compound numbers ending in 1

Numbers 2, 3, and 5 use their standard readings without consonant doubling: 二ヶ月（にかげつ）、三ヶ月（さんかげつ）、and 五ヶ月（ごかげつ）. Note that while じっかげつ is the traditional and more formal reading for 10 months, じゅっかげつ is overwhelmingly the most common pronunciation in everyday modern Japanese. Numbers 4, 7, and 9 use their standard readings: 四ヶ月（よんかげつ）、七ヶ月（ななかげつ / しちかげつ）、九ヶ月（きゅうかげつ）. To ask 'how many months?', use the question word 何ヶ月（なんかげつ）. One to three months are also frequently read using the native Japanese readings: 一月（ひとつき）、二月（ふたつき）、and 三月（みつき）. These readings are highly versatile and can carry a softer, slightly poetic, or traditional nuance suitable for both formal and casual contexts. Additionally, 'half a month' is expressed as 半月（はんつき）. Be careful not to read this as はんげつ, which means 'half-moon'. To say 'X and a half months', add 半（はん） after the counter, such as 一ヶ月半（いっかげつはん） for 'one and a half months'.

2. Writing Variants:
You will see the か part written in several ways, but the pronunciation is always the same:

• 〜ヶ月: Most common in daily life. The ヶ is a symbol derived from the kanji 箇 (or its variant 个) used as shorthand.
• 〜か月 / 〜箇月: In official government documents, guidelines state that Arabic numerals (used in horizontal writing) are paired with the hiragana か (e.g., 1か月), while Kanji numerals are paired with the kanji 箇 (e.g., 一箇月).
• 〜カ月: Uses the full-sized Katakana カ. This is the standard style for major Japanese newspapers like the Asahi Shimbun.

3. Duration vs. Calendar:
Do not confuse this with the names of months. 一月（いちがつ） is January, but 一ヶ月（いっかげつ） is a one-month period. You can add 間（かん） to the end (e.g., 三ヶ月間（さんかげつかん）) to emphasize the 'interval,' but it is not required.