コ
 
ツ
 
コ
 
ツ

adverb taking the と particle, adverb

Onomatopoeic or mimetic word.
  1. steadily, unflaggingly, untiringly, laboriously, diligently.
  2. knocking, tapping, clicking, drumming.

Variations

Pronunciation Kanji Kana Is Common
 
コ
 
ツ
 
コ
 
ツ
コツコツ ✔
 
こ
 
つ
 
こ
 
つ
こつこつ ✔