pref ‧ e ‧ ra ‧ bly /ˈpref ə rəbli/ BrE AmE adverb
[ Word Family: adverb : ↑ preferably , ↑ preferentially ; adjective : ↑ preferable , ↑ preferential ; verb : ↑ prefer ; noun : ↑ preference ]
used in order to show which person, thing, place, or idea you think would be the best choice:
Students must take two years of a foreign language, preferably Spanish.