1 Iki Piki: We can't sell our spare organs. They'll be the only thing keeping us alive when we come back in time.
1 Serron: Only one thing for it. We skip the system without paying.
2 Iki Piki: We'll be branded as criminals across an entire section of the Galaxy!
2 Serron: You mean "sector".
3 Iki Piki: No, a sector is a piece of a circle enclosed by an arc and two radii. They don't tessellate. That's a stupid way to organise a galaxy into administrational units.
4 Serron: Oh, and I suppose you've been branded a criminal across one before?

Taken geometrically, a sector really is a silly shape for splitting up a thing as large as a galaxy into administrational or navigational sub-units. You can get three or four sectors which make convenient sub-units, but each one would have bazillions (yes, that's a technical term) of stars and be of marginal utility beyond considering the galaxy as a whole. What you really want is cubical sections roughly tens to maybe hundreds of parsecs across, so each one contains a workable number of stars. You could fit about a million to 10 million such sections into a typical galaxy.

This is taking it literally of course. "Sector" has effectively been neutered of its geometrical meaning in science fiction.

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2018-11-03 Rerun commentary: Strictly speaking, what Iki Piki is defining is a sector of a circle. This makes sense for a three dimensional structure like a galaxy that is a very flat disc, as you can consider it be essentially a circle with a little bit of height. Cutting sectors of a galaxy is like cutting slices of cake.

But in 3D you can also have sectors of spheres, which are conical volumes with a spherical end cap, the centre of the sphere being at the point of the cone. Unfortunately these are even worse shapes for carving up a galaxy, as the cake analogy doesn't apply and there's no sensible way whatsoever to divide a galaxy into a number of spherical sectors. Even if our galaxy was not a spiral galaxy but was a more spherical object (which elliptical galaxies are), spherical sectors are no good, because they don't fit together to fill space - there will always be gaps between them. It's like cutting a rolled sheet of pastry into circles.