1. The cardinal number that is the sum of eight and one
   - nine, 9, IX, niner, ennead

Type of: digit, figure

• isoantibody
• isobar
• isobaric
• isobilateral
• isobutyl nitrite
• isobutylene
• isobutylphenyl propionic acid
• isocarboxazid
• isochoric
• isochromatic
• isochronal
• isochrone
• isochronous
• isoclinal
• isocline
• isoclinic
• isoclinic line
• Isocrates
• isocurvature
• isocyanate
• isocyanic acid
• isocyclic
• isodiametric
• isodynamic
• isoelectronic