A 10 mm rod (TMT bar) is a steel reinforcement bar with a diameter of 10 millimeters, used in concrete structures to increase strength and durability.

In simple words

It is:
👉 A steel stick placed inside cement (concrete)
👉 To make buildings strong, stable, and long-lasting

🔍 Key points in definition

• “10 mm” = thickness (diameter) of the rod
• Made of high-strength steel
• Used as reinforcement (support) in construction
• Usually ribbed (lined) for better grip with concrete

🏗️ Example use

When a slab (roof) is made:

• Concrete alone is weak in tension
• So 10 mm rods are added inside to handle load and prevent cracks