On grammatical class:

vi'a
dimensionality of space interval tense: 2-space interval; throughout an area.
vi'e
dimensionality of space interval tense: 4-space interval; throughout a spacetime.
vi'i
dimensionality of space interval tense: 1-space interval; along a line.
vi'u
dimensionality of space interval tense: 3-space interval; throughout a space.

In definition:

cmavrvi'a
x1 is the selma'o "VIhA".

In notes:

ve'arda
x1 is a part of Lojban text representing rule 'space-interval' according to the first edition of the book 'The Complete Lojban Language'.