1. Belonging to them

Sounds like: there's

Encyclopedia: Theirs

• tessella
• tessellate
• tessellated
• tessellation
• tessera
• tesseract
• Tessin
• tessitura
• test
• test ban
• test bed
• test case
• test copy
• test drive
• test driver
• test equipment
• test fly
• test instrument vehicle
• test match
• test paper
• test period
• test pilot
• test range
• test rocket
• test room