They precede iotas

• Angle symbols, in trigonometry
• Sorority letters
• Sorority members such as Ann-Margret and Laura Bush
• Letters after etas
• Greek characters leaving the job unfinished
• Angle symbols, in math
• Some campus sisters
• Trigonometry symbols for angles
• Angle symbols, in geometry

Wiktionary Word definitions in Wiktionary
n. (plural of theta English)