전공(을) 하- major in something

전부 the whole thing, total

전부다 everyting, all of it

전에 earlier, before

전화 telephone

전화(를) 하- make a phone call

전화(를) 거-ㄹ- make a phone call

전화(를) 받- answer the phone

전화번호 telephone number

전혀 $[$not$]$ at all