Valmiki Ramayana Ayodhya Kanda Sarga 108 Shloka 11

पिता the father, जन्तोः for a being, बीजमात्रम् is a seed only, शुक्लम् white, रुधिरमेव blood, ऋतुमन्मात्रा in the mother's womb during her menstrual period (favourable time for conception), संयुक्तम् is blended, तत् due to that, इह in this world, पुरुषस्य man's, जन्म birth takes place.

For a living being, the father is only a drop of white blood (semen). During her menstrual period this is blended in the mother's womb due to which a man is born in this world.