There are different Usages of the letter K.
1. the eleventh letter of the English alphabet
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
This letter denotes the next after J in a set of items, categories, sizes, etc. e.g. It also denotes the eleventh of eleven or more hypothetical people or things.
2. K as Knit
K 59 rows is a method to tell in knitting that how many rows are there in a pattern.
K = kilo as in Kilogram or Kilometer or Kilobytes etc. K = Kindergarten as in KG. K = Kelvin a unit of temperature. K = King in the deck of Playing Cards. K = informal Thousand.
the deck of Playing Cards. Besides, K letter of English Alphabet is used in Cambodia as International Vehicle Registration.
K = Potassium an element with atomic number 19 in the periodic table. This is a soft silvery-white highly reactive metal of the alkali metal group. Moreove, K = Boltzman's Constant which is the ratio of the gas constant to the Avogadro's constant and numerically equals to 1.381 × 10−23 where the number of molecules equals to Avogadro's number.
K = Kelvin = SI unit of thermodynamic temperature.
5. Universal Symbol of Constant
K = Universal Constant while replacing the sign of proportionality in scientific equations.
The most Common Noun which is used to learn this letter at the Nursery level is Kite; K for Kite.