I'm often asked the question if my child can be potty-trained even if he can't yet and I always say, "Yes, your child can be potty-trained, even if he doesn't have the communication to verbally tell you that he needs to go pee in the potty. That's okay."
Once your child is comfortable sitting on the potty and having successes in the potty, then you can work on how she can communicate the need to use the potty. She can learn to communicate with you by pointing to the potty, by using a picture to communicate her need to use the potty, or by using a sign to use the potty.
Other times children have been able to use an iPad or another communication device to tell the parent that they need to go pee in the potty. So either way, if your child doesn't have any language, they can still be potty-trained.
Typically, kids have language skills before they're potty-trained, but if your child is a special needs child and doesn't have communication yet, it's okay to go ahead and train them before they can communicate with you. Occasionally, young children who don't have much language yet can still be potty-trained. You can teach them how to signal you with a point or a sign or, again, they can use pictures to communicate their need to use the potty.
Whether your child is 18 months or five years old, it doesn't matter if they have the language to communicate with you, they can still be potty-trained.