The most common two letter combinations are called as digrams. e.g. th, in, er, re and an. The most common three letter combinations are called as trigrams. e.g. the, ing,and, and ion.
Civil Services Day is celebrated in India every year on 21st April. The Union Home Minister Shri Rajnath Singh inaugurated the two-day 11th Civil Services Day program (20-21 April) in New Delhi.