major in
https://gyazo.com/3fc97c11ea01036a566b5ce254ce0ad5
source: Wolf Children Ame and Yuki
verb no object (major in) North American & Australian/NZ
specialize in (a particular subject) at college or university:
⦅米・豪⦆ (大学で) 【学科を】専攻する «in» (→ specialize, minor)
e.g. I was trying to decide if I should major in drama or English.