Miniature means very very small for a thing of its kind. Something which is miniature could be called small but generally miniature is something which is extremely small. Also, it is important to note - miniature means a very small version of something of its kind - for example a miniature horse. You would not call anything that is small, miniature, but you can call anything that is miniature small (hope I'm not confusing you) - you would only call something miniature if it was much smaller than the typical size for something of its kind - e.g. a miniature house (a doll house for example). Some examples - My neighbour drives a Nissan Micra, his car is small. My mother drives a Range Rover, her car is big. My brother has a toy car, it is a miniature version of my mother's Range Rover. I could go into more detail, but I worry that I'm already making it too confusing, hopefully someone can give you a clearer answer if you don't understand what I mean.