I'm not so sure about that.

not Adverb

— "Not" makes the verb of a sentence have the opposite meaning. I was not there. I am not fat!

not Conjunction

— The item before "not" is more correct or better than the item after "not". I wanted tea, not coffee! Meaning: I wanted tea. I did not want coffee. It's stupid, not funny. Meaning: It is stupid. It is not funny.

not Interjection

— Used to indicate the sentence before is sarcastic or ironic. This means that the sentence has the opposite meaning. I like doing lots of boring homework. Not! Meaning: I do not like doing lots of boring homework.

so Adverb

— How much; very much. The box was so wide that the person was not able to take it through the door.

so Preposition

— With purpose. Saying the reason why someone does something. The person locks the door so no one is able to come in and take things. We help them so that they can get better.

sure Adjective

— When you are sure about something, you are certain. The student was sure that his answer was correct.

about Preposition

— You use about to say what subject something is related to. Let's not talk about her problems. — If something moves about, it moves this way and that way. He walked about the place, looking everywhere. — Having to do with, concerning, regarding. I will talk about dogs.

about Adverb

— You use about before a number or amount, to say that it may be a little more or a little less. We're here just about every week. About two years ago, I started skiing.

about Adjective

— Something is about to happen, it will happen very soon; almost going to happen. Please be seated. We're about to begin.

that Determiner

— Used to show which thing we are talking about; used with things that are not close to the speaker. Give me that book, not this one. Give me that, not this. That dog is hungry.

that Subordinator

— used to link a subordinate clause to a main one You said that you liked me. Give me the book that I dropped.