The term 'triangle ratio' refers to the ratios of the sides of a triangle to one another. The two most common ratios are SINE (4 letters) and COSINE (6 letters). SINE is the ratio of the length of the side opposite an angle to the length of the hypotenuse, while COSINE is the ratio of the length of the side adjacent to an angle to the length of the hypotenuse. These ratios are important in trigonometry and geometry, and are used to calculate angles and distances.