The distinction of PT,NPT,G and standard thread

NPT, PT and G thread are all Pipe thread.
NPT is the abbreviation for National (American)Pipe Thread, It belongs to the American standard 60-degree taper pipe thread and is used in North America. China standards can be found in GB / T12716.

PT is the abbreviation for Pipe Thread. It is a 55 degree sealed conical pipe thread. It belongs to the Wyeth thread and is mostly used in Europe and the Commonwealth of nations. Commonly used in the water and gas pipe industry, the taper is specified as 1:16. China standards can be found in GB / T7306.
G is pipe thread with 55-degree thread angle where pressure-tight joints are not made on the treads, belongs to Whitworth thread. Marked G stands for the cylindrical thread. China standards can be found in GB / T7307.
Metric threads are represented by pitch, and American and British threads are represented by the number of threads per inch. This is their biggest difference.
The metric thread is a 60-degree equilateral tooth shape, the inch thread is an isosceles 55-degree tooth shape, and the American thread is 60 degrees.
Metric units are used for metric threads, and British units are used for US and British threads.
The common thread: Metric thread–M; inch thread–W; US thread—UNC、UNE、UNEF.
The pipe thread: Inch thread—PS、PT、PF; US thread—NPS、NPT、NPTF、NPSM.