円周
えんしゅう · enshuu · JLPT N2 · noun
circumference
🛞 円周 = circle + lap around: the distance once around a circle
円 (en) means circle, as in the yen coin. 周 (shuu) means a lap or circuit, as in 一周 (isshuu), one lap. So 円周 is the circle's lap, its circumference. The same 周 shows up in 円周率 (enshuuritsu), pi.
周 — enclosure 囗 + 吉 (earth 土 + mouth 口)
Originally a pictograph of a field with grain plotted in rows, suggesting density and completeness. It came to mean 'all around,' 'circumference,' and 'complete,' later extending to 'week' (a full cycle). Also a major surname, famously the Zhou dynasty.