Affirmative sentences are simple sentences and shows positiveness, also called assertive sentence. Negative sentences are those sentences that lacks of positiveness, also called non-affirmative or non-assertive sentence. Thank you

affirmative means the sentence has the attribute of telling the person 'what you have said is correct, or the question you have asked has an answer that is positive. An affirmative answer needs a question where there is an assumption, or suggestion that the asker is wanting to check some information. An example question: 'Are you going to the cinema tomorrow?' Affirmatives: 'yeah, i'm going to see ...' 'uhuh, really looking forward to it' 'sure, do you want to come too?' 'I go every tuesday' 'I plan to, unless something comes up' some negative responses 'sadly no, i must work' 'actually, there is nothing on that i want to see' 'no, i have to meet my mum' 'i wish i could but i have to work' You cannot give an affirmative answer to an 'open' question such as 'What are you doing tomorrow night'. This type of question is not trying to check what the speaker knows, it is asking for information with no suggestion.