Why cats sometimes make baby cry sound?

Why do cats "cry"?
I often hear cats outside making baby cry sound during the night.

During the day, I have seen many cats at different places but I have never hear anything like it.

How do you explain this behavior?

It depends on the vocabulary they're using. Night id prowling time. They're talking to each other, not to us. Though, what I hear outside is not "baby cries". More like screaming. I think it translates as, "This is MY turf! GET OUT!!!" A female in heat, or a male looking for a female in heat will tend to wail and whine. My first spring in this house I had a male cat come around "courting" my (fixed!) female cat, "singing opera" under my windows. Cats don't generally meow at each other. They have a vocabulary trills, chirps, and "fightin' words", but they save the meows for us humans because they have discovered we don't pay attention if they don't. They seem to be very smart about figuring out what will get our attention best, whether it's a meow, or knocking something off a shelf. My first cat, Tiro, learned to speak Human very well. One time he wanted to go out and went to the back door while I was in the kitchen. We had a conversation.
"NGOW!"
"No. You can't go out right now."
"Ngow?"
"I said NO!
"mrph." And he walked away. No translation needed.

They do make both "baby cries" and screaming at night. yeah I know when they scream it is most likely they are getting into a fight. I just don't know about what the "baby cries" mean.

They indeed can understand quite some human vocabulary. I have read it somewhere that the cats can understand some of the words from the specific language the owner speak. If the cat is adapted by another family who speak a different language, then the cat will slowly forget about the original owner's language and start to get used to the new language.

All three of my cats have different "voices". I can tell by the sounds what they are doing, if two of them are "wrestling", and which two it is. And I can if two of them are actually "fighting", which is pretty rare, and which ones it is just by the sounds.

I've had cats all my life, I think they may understand specific words, but they definitely understand they sound of your voice if you've had them awhile. Mine know the sounds of our voices if we are feeding them, playing with them, scolding them, warning them, etc... Some people think they know their names, maybe, but I think they know the sound of your voice when you are calling them. Have a complete stranger call the same name and you will get no response normally.

That is interesting. I never thought about it. Yeah, almost all cat owners name their cats, and many of them think the cats know their own names.

I have found with younger cats what you call them doesn't matter too much. "Cats don't care what you call them as long as you call them for dinner." I adopted a 15 year old cat who had been named Alley (as in; Alley Cat). I thought she had too much class to be an alley cat, so I changed her name to Abbey because the similar sound wouldn't confuse the cat. Then there was my third cat, who I think thought his name was Max-get-off-of-there!

I know what you mean about "cries" though. Some cats can sound uncanily like a baby or small child. I have been startled some times when I thought I heard a cat in my yard, only to discover it was one of the kids accross the alley. I don't know exactly what the cats are saying, but I think this pleading meow is to get our attention. Whether they mimic this tone intentionally or it's a survival trait from Mother Nature, I don't know.