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A series and B series.J. M. E. McTaggart’s labels for two ways we have of ordering occurrences in time. The A series is indexical, agent-centered. Just as “here” refers to the current spatial location of the speaker, “today” refers to the speaker’s temporal location. Yesterday, today, and tomorrow belong to the A series. The B series locates occurrences in relation to one another in time, not relative to the speaker. Unlike something’s being here now, something’s occurring before, after, or simultaneous with another is eternally true, not indexed to the spatial and temporal location of the speaker.Four-dimensionalism.As used here, the phrase refers to conceptions as “spacelike,” a dimension in addition to the three spatial dimensions. An object persisting through time is extended both spatially and temporally.Temporal part.Used here to refer to an object at a time or over a stretch of time. You yesterday, you today, and you tomorrow are temporal parts of you in the way your left half and right half are spatial parts of you. On this conception of temporal parts, objects persisting over time are not made up of temporal parts. Objects’ temporal parts are ways of dividing up whole objects analogous to dividing Earth into Southern and Northern hemispheres. Thus conceived, spatial and temporal parts are not to be confused with the material occupants of a spatial region or temporal interval.