a·pe·ri·od·ic 
(ā′pîr-ē-ŏdĭk)
(ā′pîr-ē-ŏdĭk)adj.
Occurring without periodicity; irregular.
a′pe·ri·odi·cal·ly adv.
a·pe′ri·o·dici·ty (-ə-dĭsĭ-tē) n.
- interstellar medium
- interstice
- interstitial
- interstitially
- intertestamental
- intertextual
- intertextuality
- intertextually
- intertexture
- intertidal
- intertidally
- intertitle
- intertribal
- intertropical
- intertropical convergence zone
- intertwine
- intertwinement
- intertwist
- interurban
- interval
- intervale
- intervalic
- intervallic
- intervene
- intervener