Give the definition of sidereal, true solar and mean solar time.

Sidereal time is the time elapsed from the moment of the upper culmination of the vernal equinox to any other position, expressed in fractions of a sidereal day (sidereal hours, minutes and seconds). True solar time is the time elapsed from the moment of the lower climax of the center of the Sun to any other position, expressed in fractions of a true solar day (true sundial hours, minutes and seconds). Average solar time is the time that is determined by changes in the hour angle of the average equatorial Sun – a fictitious point moving uniformly along the celestial equator at the average speed of the true Sun along the ecliptic and making a full revolution during the year.