In ordinary language, the meaning of sun salutation is taken as a salutation to the sun. The practice of sun salutation is being done since ancient time. This is a gift of Vedic age man. In the ancient time, the sun was regularly worshipped as daily rituals because the sun is the symbol of spiritual consciousness.
In the traditional sun salutation posture, seven postures are arranged in a rhythmic way in 12 positions which are considered half chakra (repetition). To complete it, 24 positions are required to be performed when it is called full cycle (repetition). Since the ancient time, these seven postures are practiced in sun salutation.
In India, these seven postures are related to seven chakras. As there are 24 hours in a day, similarly there are 24 positions for full chakra in sun salutation.