1. A ruler, with a cross-piece at one end, and shaped like a T.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• r square,
• f square,
• g square,
• y square,
• 6 square,
• 5 square,
• t aquare,
• t zquare,
• t xquare,
• t dquare,
• t equare,
• t wquare,
• t s1uare,
• t s2uare,
• t swuare,
• t sauare,
• t sqyare,
• t sqhare,
• t sqjare,
• t sqiare

The adjective form of the word "T square" would be "T-square" itself, as it is already an adjective form that describes a type of ruler.

The plural form of the word "T square" is "T squares"

The singular form of the word "T square" is "T square". It remains the same in both singular and plural form.