Point 4. Some uses of thaּN

English ภาษาไทย
 I want to send this letter via airmail.  ผมอยากจะส่งจดหมายฉบับนี้
 He wants to go engage in inspection
 along medical lines ('in the way of medical

The word
thaּN, whose primary meaning is 'way, route', is also frequently used as a preposition with the meaning 'by way of, via, in the way of', as shown above.