For Big/Small there is "Size".
For Long/Short there is "Length".
Whats the grouping word for Intra/Inter?
Intra means "inside" and inter means "between" (and extra is "outside") so I suppose location might as good as anything.
However, big, small, long and short are all adjectives. Long and short describe length; big and small describe size. Intra and inter are not adjectives — you can't use those words in the same way as the others — and so trying to group them is not really the same thing.
However, inter-planetary dust, or travel, is between the planets; extra-mural activity covers lessons outside the walls of the school; intranet is a network within a company. location may well work.
These are known as locational prefixes, so you can describe them as locational. If you need a noun to use as your "grouping word," you could use locational prefixes or simply location.