Reference point

This is the point in the nucleus angle profile used to anchor the profile for alignment. It is the point most robustly detectable when the morphology is abnormal. In rodent sperm, the reference point is the tip of the hook. In sperm from other species, the reference point is the head of the nucleus. In round nuclei, the reference point is one of the points on the longest axis.

Orientation point

This is the point used to orient nuclei when drawing them, for example in the consensus nucleus and the nucleus composite. In sperm, the orientation point is the tail attachment point. In round nuclei, the orientation point is the longest axis point opposite the reference point.

Top and bottom vertical points

These are features that can be found in a mouse sperm nucleus. They define the flat segment underneath the hook of the nucleus, and are used to orient nuclei vertically for display and for bounding box calculations.

Border tag

Any of the points around the border of the nucleus can be tagged with one or more labels. This is called the border tag. Examples include the reference and orientation points. The border tags in a nucleus are listed in the Cells tab in the cell information table.