Newborn kittens (up to 2 weeks old) are completely dependent on their mother for food, warmth, and stimulation. Without a mother, they will not survive.
Kittens between 2 and 4 weeks old can begin to lap liquid food, but they still need their mother's milk for complete nutrition. They also need help staying warm and stimulated. With careful hand-rearing, kittens this age can survive without their mother.
Kittens between 4 and 8 weeks old are more independent and can eat solid food. However, they still need human care and socialization to develop properly. With proper care, kittens this age can survive without their mother.
Kittens over 8 weeks old are usually able to survive on their own, but they still benefit from human companionship and socialization.
If you find a kitten without its mother, it is important to take it to a veterinarian as soon as possible. The veterinarian can assess the kitten's health and recommend the best course of care.