What are some seven-letter shapes?

23 of the 148 shapes in Icillion have exactly 7 letters, for example Hexagon, Octagon and Rhombus.

Which seven-letter shapes start with A?

A is the most common first letter here, with 3 names, such as Annulus, Arbelos and Astroid.

Science · lists

23 seven-letter shapes in alphabetical order, from “Annulus” to “Trefoil”. Each one counts as an answer in Icillion.

23 of the 148 shapes have exactly 7 letters (16%).
Most start with A (3), C (3) and S (3).
Only names of one word are counted, and only their letters: spaces, hyphens and apostrophes are not.

What are some seven-letter shapes?: 23 of the 148 shapes in Icillion have exactly 7 letters, for example Hexagon, Octagon and Rhombus.
Which seven-letter shapes start with A?: A is the most common first letter here, with 3 names, such as Annulus, Arbelos and Astroid.

How deep does your knowledge go?

Seven prompts a day, twenty seconds each. Obvious answers float on the tip of the iceberg; rare ones sink all the way to the trench.