Pawns, e.g

• Quartet x two
• Pizza slices, often
• Rowing team quorum
• Series of eight
• Pie slices, often
• Two tetrads
• Group of eight
• Slices in a pie, often
• The planets, since Pluto's downgrade

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Octad \Oc"tad\, n. [Gr. ?, ?, the number eight.] (Chem.) An atom or radical which has a valence of eight, or is octavalent. A group of eight things.