counter for Sino-Japanese words
Attaches directly to a number and precedes the noun being counted. Common with months (か月), places (か所), countries (か国), etc. Often written as ヶ or ケ in compounds.
I moved three months ago.
He studied abroad in America for three months.
This building has five entrances/exits.
There are three mistakes in this text.
She traveled to five countries.
つ is the native Japanese general counter used with kun-readings of numbers (ひとつ, ふたつ), whereas か attaches to on-yomi numbers in Sino-Japanese compounds such as 三か月.
か and 個 look and sound related as generic counters, but か attaches to Sino-Japanese counting compounds like か月・か所・か国, while 個 is the everyday counter for small discrete objects.
The most common spelling; usually written in kana.
Katakana variant, often seen in signs or stylized writing.
Small ke form, commonly used in place names and some counters (e.g., ヶ月, ヶ所).
Full-size katakana ke, sometimes used as a variant of ヶ.
Formal kanji, rarely used in modern writing.
Rarely used kanji form for this counter; usually read こ.
Archaic variant, almost never used.
Derived from the kanji 箇 (ka), a counter for items. The small ke form ヶ is a simplification of 箇, and か is the phonetic reading.