Word:-
The group of letters which makes any meaning, is called word.
Examples,
1) He, 2) you 3) Book 4) Master.
each of these words are made up of different letters. that is called word.


Sentence:-
A group of words which makes complete sense is called a sentence.
Examples,
1) I read a book. 2) You go to school.
3) This is a cat 4) Ahmed is playing football.