For example, learn K-theory:
K is the letter which kilo starts with. Kilo is the prefix for one thousand (e.g. kilogram, kilometer, kilowatt, etc.).
If you mean in baseball, K is for strikeout, from the letter in the word.
How about a kite which is a 4 sided quadrilateral.
It can stand for many things. One possibility is the vertical axis in solid (3-dimensional) analytical geometry.
4 letter word that starts with k
A sweet word that starts with K is kisses (Hershey's).
K
Kudos is a five-letter word for award, but it starts with k.
kite
kill
kitty
· knowledge
KANGEROOS
Kool
Killer
kicks!