What is the difference between the right ascension and declination of a star, and it's altitude and azimuth?

In astronomy, the declination is the angle that forms a star with the celestial equator. It is one of two coordinates of the equatorial coordinate system, the other coordinate is the right ascension. The declination is measured in degrees and is positive if it is north of the celestial equator and negative if it is to the south. The declination is comparable to the geographical latitude In astronomy, the right ascension is one of the astronomical coordinates that are used to locate the stars on the celestial sphere, equivalent to the terrestrial length (geographical coordinate). The straight ascension is measured from the Aries point in hours

Well, a and b together would be negative. b alone would also be negative.