A string is a fibre designed to hold things together whereas a thread is that which weaves through. A thread is now, the string potential.

A string maybe more substance than a thread, but the more subtle and fine thread shows a bond by relativity not by mass and restriction.

A string binds from the outside the thread internally. The thread is an inherent part of the fabric is not and external bond.

Both words are often used outside such common meaning and can refer to any actions or thoughts that are common or join in some manner many otherwise individual object, properties or events. String theory, topic and message threads.

The string theory is not the thread theory. There may be many strings in the universe but only one thread.

The thread of life the strings of time. The Thread is the connection not an action of binding and boundaries.

The thread weaves throughout life whereas the strings of DNA separated plants from animals for example.

The thread is a common factor, string can hold diverse objects by force.