You can judge the specific age of a cat by looking at its teeth. Generally, a cat between 2 and 4 months old has all its deciduous teeth. A cat between 4 and 6 months old is in the period of tooth replacement or has completed tooth replacement. By 2 years old, a cat's teeth have been completely replaced. The teeth of cats aged 3-5 years old will be relatively white and have some tartar and wear. Cats with more severely damaged teeth are mostly aged 6-10 years old.