navigate, sail, cruise, fly
コウ / —
empty, sky, void, vacant, vacuum
クウ / そら
eaves, roof, house, heaven
ウ / —
mid-air, air, space, sky, memorization, interval of time
チュウ / —
craft, construction, katakana e radical (no. 48)
study, learning, science
ガク / まな.ぶ