Sikhs use Singh and Kaur to distinguish who is male and who is female:

Singh (lion) is used for a male Sikh because a man is regarded to have similar characteristics for example bravery, courageous, sovereignty, muscular pyshique, considerate, responsible, energetic, humble and with uncut hair.

Kaur (princess/lioness) is used for female Sikhs because they have similar characteristics, beauty, sweet natured, loving, compassionate, delicate, chaste, respectful, and the serenity of a princess who will one day be a Queen.