In string theory, a string is considered a fundamental object. It is a one-dimensional entity that can vibrate and interact with other strings. While strings are described as "fundamental," it doesn't necessarily mean they are indestructible in the sense of being unbreakable.
The concept of breaking a string in string theory is not the same as physically snapping a string like you would with a piece of rope. When we say a string can "break" in the context of string theory, we mean that it can undergo a process called string splitting or string interaction, where a string can split into two or more separate strings or combine with other strings to form new structures.
The splitting or interaction of strings is a fundamental feature of string theory, and it plays a role in the dynamics and behavior of the theory. Strings can join together or split apart, and these processes contribute to the rich and intricate interactions that occur within the theory.
So, while strings in string theory can undergo processes that resemble breaking or splitting, it is important to note that these processes occur within the mathematical framework of the theory and should not be directly equated to the physical breaking of everyday objects.