Many differences
The Patriot was first designed as an anti-aircraft missile with the secondary mission of defending against short ranged missiles. A Patriot missile battery only protects a fairly small land area. THAAD is designed primarily for theater defense against short to medium ranged missiles. It can defend a much larger land area than the Patriot. It has a bi The NMD missile is designed to go after ICBMs. These missiles travel much faster than short ranged tactical missiles. The interception has to take place much further from the launch site to protect the widest possible land area.