► 名詞周囲  [(1)しゅうい]    
meaning:  circumference  rank: 2☆ 
頭の周囲の
長さ ⇨ The circumference of a head. A head size  
(☛ Not interchangeable with 周辺 in this sense)円周  [えんしゅう]    
meaning:  circumference  rank: 4☆ 円周は
直径掛ける
パイで
求まる ⇨ The circumference will be calculated by multiplying the diameter with pi