̷ ̷ˌ ̷ ̷ ̷ ̷ˈlāshən noun
( -s )
Etymology: Middle French or Latin; Middle French, from Latin intercalation-, intercalatio, from intercalatus (past participle) + -ion-, -io -ion
1.
a. : the insertion of one or more days at regular intervals in a calendar in order to bring it into accord with the solar year
b. : a period so inserted
2.
a. : the insertion or introduction of something among other existing or original things
b. : something that is so inserted
the poet was reluctant to vary the metrical arrangement of the poem to accommodate an intercalation — A.K.Moore
3. : the introduction or existence of a bed or layer between other layers or of a particular fossil horizon between fossil zones of different character ; also : an intercalated bed or lenticular deposit
a few lenses of volcanic ash are present as intercalations