やっつ (yattsu) is the kun-yomi when counting things.
ハチ (hachi) and ハッ (hatsu) are the on-yomi readings. ハチ is used in compounds like 八月 (はちがつ, hachigatsu: August).
As part of proper names and set phrases, readings may vary; learn common expressions like 八日 (ようか, yōka: the 8th day of a month) or 八百屋 (やおや, yaoya: vegetable shop).
Examples
Kun-yomiNative Japanese Readings
八つください。
Eight, please.
Uses kun-yomi やっつ (yattsu) when counting things
八つあります。
There are eight.
Uses kun-yomi やっつ (yattsu) when counting things
On-yomiSino-Japanese Readings
八月
August
Uses on-yomi ハチ (hachi) in compound for months
八月にいきます。
I will go in August.
Uses on-yomi ハチ (hachi) in compound 八月
ExceptionIrregular Readings
八日
the 8th day of a month
Exception: 八日 reads as ようか for the eighth day of the month
八百屋
vegetable shop
Exception: 八百屋 reads as やおや (vegetable shop)
Quick facts
Radical: 八 (itself)
Strokes: 2
Common compounds: 八月 (はちがつ, hachigatsu), 八百屋 (やおや, yaoya: vegetable shop)
⚠️ Exceptions:
八日 reads as ようか when meaning "the 8th day of a month".