Why does my cat keep meowing?
A cat that keeps meowing may be hungry, sick, in heat, unfamiliar with its surroundings, or old. 
1. Hunger
It's not surprising that cats sometimes meow when they're hungry; in some ways, this behavior is normal. Cats may meow moderately when their food is opened. However, if your cat suddenly starts meowing while eating or all day long, take it to the vet to make sure its health hasn't changed.
2. Disease
A cat may make unusual meows. A weak, listless meow may indicate illness. It may also be lethargic and unwilling to move. Its large eyes may have lost their luster, and it may not look well.
3. Estrus
When cats are in heat, they will constantly meow in an attempt to attract the attention of the opposite sex. This is called the estrus cycle. A cat's estrus cycle generally begins around 6 to 10 months of age. Male cats usually go into heat once a week, with each heat cycle lasting seven to ten days. Female cats go into heat once every 2 to 3 weeks, with each heat cycle lasting 3 to 6 days. The frequency of heat cycles can vary depending on breed, environment, physical condition, and age.
4. Unfamiliarity with the environment
If you move to a new place or a newly purchased cat arrives in a new environment, it may feel uneasy and scared due to the unfamiliarity and keep meowing.
5. Getting old
Older cats may suffer from mental confusion or cognitive impairment due to age, becoming disoriented and often crying or howling inexplicably.
