Tank top or shirt
An undershirt, shirt or tank top, a piece of underwear nowadays also as a top that is worn to keep the upper body warm. Usually a undershirt has no sleeves and often it is solid in color. An undershirt is worn directly on the skin and under a different (decorative) garment, for example a shirt or sweater.
It is also called a "singlet" or "singletje". The English name, "tank top", which is sometimes used in the Netherlands and Belgium, also applies to an undershirt (undergarments, mainly for men) and a top (outerwear, especially for women).