Tensor theory is a way of understanding how different things interact with each other and change over time. Engineers use tensor theory to figure out how different materials, like steel or concrete, will behave when they're put under certain conditions or in different environments. Engineers can figure out how these materials will act when they're put under pressure or stretched, or when they're exposed to heat. They can then use this information to design and build better structures, machines, and products that are more durable and reliable.