Pith

The essence of something.

A cross section through a shoot of elderberry (Sambucus nigra) showing the whitish pith (noun sense 1.1) in the centre.A magnified cross section through the stalk of a flax plant (Linum usitatissimum) showing its pith (noun sense 1.1; number 1).The inner portion of an orange peel showing its white pith (noun sense 1.2) or albedo. The noun is derived from Middle English pith, pithe (“soft interior; pith, pulp”) [and other forms], from Old English piþa [and other forms], from Proto-Germanic *piþô, from earlier *piþō (oblique *pittan); further etymology unknown. Doublet of pit (“seed or stone ins

marrow, medulla