periodicity

n. 定期性,周期性,周期数

perfume, perfumed, perfumer, perfumery, perfunctorily, perfunctoriness, perfunctory, pergola, perhaps, peri-, perigee, perihelion, peril, perilous, perimeter, period, period piece, periodic, periodic table, periodical, peripatetic, peripatetically, peripheral, peripherally, periphery, periphrasis, periphrastic, periphrastically, periscope, periscopic, perish, perishable, perishables, perished, perisher, perishing, peristyle, peritonitis, periwinkle, perjure,