Developmental Delay: This is the most likely diagnosis, as it is a common and broad term that encompasses a range of delays in achieving developmental milestones, including gross motor skills like walking. A delay in walking can be due to various factors, including premature birth, low birth weight, or genetic predisposition.

Muscular Dystrophy: A group of genetic disorders characterized by progressive muscle weakness and degeneration, which can lead to delayed or absent walking.
Cerebral Palsy: A neurological disorder that affects movement, muscle tone, and coordination, often causing delays in achieving motor milestones like walking.
Down Syndrome: A genetic disorder that can cause developmental delays, including delays in walking, due to intellectual disability and physical characteristics.
Orthopedic Conditions: Conditions like hip dysplasia or clubfoot can cause pain or discomfort while walking, leading to a delay in independent walking.

Spinal Cord Lesions or Tumors: Although rare, spinal cord lesions or tumors can cause significant motor delays, including a delay in walking. Early detection is crucial for treatment and prevention of long-term damage.
Infectious or Inflammatory Conditions: Conditions like meningitis or encephalitis can cause acute neurological damage, leading to delayed motor development, including walking.
Metabolic Disorders: Certain metabolic disorders, such as Pompe disease, can cause muscle weakness and delayed motor development.

Duchenne Muscular Dystrophy: A rare genetic disorder that causes progressive muscle degeneration, leading to delayed walking and eventual loss of ambulation.
Prader-Willi Syndrome: A rare genetic disorder that can cause developmental delays, including delayed walking, due to hypotonia and feeding difficulties in infancy.
Rett Syndrome: A rare genetic disorder that affects brain development, causing severe intellectual disability, motor dysfunction, and delayed or absent walking.