芯 - wick

wick; marrow; staple (for stapler); (pencil) lead; stuffing; pith

wick of a candle

mechanical pencil lead

pencil lead case (for a mechanical pencil)

cardboard tube

lead pointer (for a clutch pencil); lead sharpener

to get to the heart of the matter; to get to the core

staple (for a stapler)

apple core; core of an apple

lamp wick

spare pencil lead; pen refill (cartridge); replacement wick (e.g. of a lantern)

lead of a pencil