Sentence:  mmf in a synchronous machine may be split up into two components—one along the pole axis or direct axis and the other at right angles to this or the <WSD>quadrature</WSD> axis....In the case of salient pole construction, however, the reluctances of the magnetic circuits on which the mmfs act are different along the direct axis and the <WSD>quadrature</WSD> axis. 
Meaning of the word marked with <WSD> tags:  The condition in which the phase angle between two alternating quantities is 90°.