加法 is read as かほう (kahou) and means addition.
かほう
kahou
かほうていり
trigonometric addition formulas
かほうてき
additive
かほうてきしゃぞう
additive mapping
かほうぐん
additive group
かほうこんしょく
additive mixture of colors
かにゅう
joining (a club, organization, etc.)
かこう
manufacturing
かそく
acceleration
くわわる
to be added to
かがいしゃ
perpetrator
かじゅう
weighting (in averaging)
くわえる
to include