What is the most useful and helpful word in english language?

i think 'hellow' is the most useful and helpful word in our daily life. we can greet any new people with this word and it shows dearness and closeness with each other when they greet.hellow is used as greeting and expression of surprise.hellow is often often used when answering the telephone, or as an informal greeting. Students learning a new computer programming language will often begin by writing a "Hello, world!" program, which outputs that greeting to a display screen or printer. so i think hellow word is useful in many forms for us.

The most important helpful words in English are: 1. Please 2. Hello 3. I or me 4. Yes or No 5. Ok

i think thank you is the most useful and helpful word... :)