grammar_K

kind of or sort of : of is weak form. it can be put anywhere in a sentence. it is oral english. not an idiom
kind: a lot of possible usage. we can say i have two kinds of solutions. or solution. we can also say these or those kind of  ....we can also say apples of this kind/sort/type.
know: he knows how to swim , not swimming./ know means understand. e.g. he knows to water the plants.


knot: undo..the knot
keep up:
to continue without stopping or changing, or to continue something without allowing it to stop or change
  Keep up the good work!
He does not know a thing= he does not know anything