A T-shirt is a simple, casual shirt made of lightweight, stretchable fabric, typically cotton or a cotton blend, in the shape of the letter "T" when laid flat.

Key characteristics include:

• Sleeves: Usually short-sleeved, but long-sleeve variations exist.
• Neckline: Most commonly a round crew neck or a V-neck.
• Material: Known for comfort and breathability due to the soft knit fabric.