Calculate, plan

계산 = calculation
합계(하다) = total, to add up
시계 = watch (timepiece) 
계획(하다) = plan

Continue, adopt 

계속(하다) = to continue
계모 = stepmother
계부 = stepfather

Rank, stairs

계급 = rank, class
단계 = stage of development
계단 = stairs

Season

계절 = season
사계 = the four seasons
동계 = the winter season
하계 = the summer season

Mother

부모 = parents (부 = man, husband, male)
모국 = one’s native country
모국어 = one’s native language
모자 = mother and Son
모녀 = mother and Daughter
미혼모 = an unmarried mother
모유 = mother´s milk, breast milk
계모 = a stepmother

Shape

모양 = shape, form
모습 = appearance
외모 = appearance
용모 = features, looks
미모 = beautiful face

Copy

모방(하다) = imitate
모조품 = imitation, fake
모형 = mock-up, model