These can accommodate one child or one adult sleeper although the length of the mattress might be too short for an adult. Twin size mattresses are used for children's rooms. bunk beds, daybeds and smaller spaces such as guest bedrooms.
These mattersses area great space savers and are commonly found in dorm rooms and offer an additional five inches of length to your sleeping space.
FULL (OR DOUBLE)
These provide more width for your sleeping area. A full size mattress is ideal for one person. If you divided the mattress in half two people would only have 27 inches of sleep space (or the equivalent of a crib mattress).
These mattresses are also great space savers and are commonly found in dorm rooms and offer an additional six inches of length from the standard FULL mattress.
If you prefer more living space in your master bedroom, a queen size might be what you are looking for. Also, queen mattresses are ideal for someone who likes additional width and height while sleeping; which makes it a great choice for growing children and taller adults.
If you have the space in your bedroom, a king size mattress is the best choice for couples; you each have a sleeping service equivalent to a twin extra long mattress. It is also great for growing families or pet owners.
If you are looking for additional length in your sleep surface, a California King might be what is right for you. Four inches of width are taken from a traditional king mattress and added to the length.