偏芯[henshin] eccentricity (in mechanics, electronics, etc.)
燈芯[toushin] (lamp) wick
帯芯[obishin] thick obi sash
摘芯[tekishin] thinning (buds and branches)
芯地[shinji] padding

替え芯[kaeshin] spare lead
鉛筆の芯[enpitsunoshin] lead of a pencil
硬の芯[kounoshin] hard pencil lead
林檎の芯[ringonoshin] core of an apple

遺跡[iseki] historic ruins (remains, relics)
刈り跡[kariato] cut-over land
監査証跡[kansashouseki] audit trail
奇跡的[kisekiteki] miraculous
軌跡[kiseki] tire track

形跡[keiseki] traces
跡始末[atoshimatsu] settlement (of affairs)
跡片付け[atokatazuke] tidying up
航跡[kouseki] wake (of boat)
痕跡[konseki] trace